Process for the separation and purification of a mixed diol stream

ABSTRACT

Disclosed is a process for the purification of a mixed diol stream. The mixed diol stream comprising two-, three-, and four-carbon diols is separated into component diols by extraction with a hydrophobic solvent mixture. The diols recovered in the extractant may be removed from the extractant stream by back extraction with water or by distillation with an azeotrope-forming agent present, preferably an azeotroping agent already present in the extractant mixture.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a Divisional of U.S. application Ser. No. 13/431,308filed Mar. 27, 2012 now United States Publication Number 2012-0184783which is a Continuation-In-Part of U.S. application Ser. No. 12/889,065,filed Sep. 23, 2010 now U.S. Pat. No. 8,466,328, which claims thebenefit of U.S. Provisional Application No. 61/374,850, filed Aug. 18,2010, all of which are incorporated herein by reference in theirentireties.

FIELD OF THE INVENTION

This invention relates to a process for the purification of a mixed diolstream. More specifically, this invention relates to the separation oftwo-, three-, and four-carbon diols. One aspect of this inventionrelates to a process for the purification of ethylene glycol by theseparation of propylene and butylene glycols. Another aspect of thisinvention relates to the separation of mixtures of propylene glycolsfrom butylene glycols. Further, this invention relates to a processwherein a mixed diol stream may be separated by extraction or extractionand distillation processes.

BACKGROUND OF THE INVENTION

Two-, three-, and four-carbon diols, as exemplified by ethylene glycol,1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol,1,3-butanediol, and 1,4-butanediol, find use in a myriad of industriallyimportant polymers and formulations. Many processes have been disclosedfor the production of these diols. For example, ethylene glycol can beproduced by the hydrogenation of glycolic acid, glycolic acid esters,methyl glycolate, oligomers of glycolic acid, oligomers of glycolic acidester, or mixtures thereof with a ruthenium compound such as, forexample, a ruthenium-organophophorus coordination compound, that issoluble or partly soluble in the reaction mixture. Such a glycolicacid-based route has been described in the art as disclosed in U.S. Pat.No. 7,615,671. The hydrogenation of glycolic acid species may alsoproduce by-product higher diols, primarily 1,2-propanediol and1,2-butanediol, in small quantities, e.g., typically less than 1 weightpercent of each compared to ethylene glycol.

Carbohydrate feedstocks also may be used to produce mixed diol streamswith varying amounts and particular species of two-carbon diols,three-carbon diols, four-carbon-diols, and higher diols.

It is desirable to separate the mixed diol stream into its componentdiols in a most economic manner. Distillation, a common method ofseparation, can prove difficult when components have close boilingpoints. The normal boiling points of ethylene glycol, 1,2-propanediol,and 1,2-butanediol are 197.1° C., 187.7° C., and 196.5° C. respectively,and ethylene glycol and 1,2-butanediol are known to form a minimumboiling azeotrope, precluding complete separation by single-feedordinary fractional distillation. Separation of such mixed diol streamsinto pure fractions by ordinary single-feed fractional distillation isextremely difficult, if not impossible due to numerous azeotropes andclose boiling points.

There is a need for a process whereby a diol mixture can be separatedinto pure fractions in an efficient and cost-effective manner.

SUMMARY OF INVENTION

We have discovered that a mixed diol stream can be efficiently separatedinto component fractions by extraction. One embodiment of our invention,therefore, is a process for recovering purified ethylene glycol from amixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 1 weight percent to 99.5 weight percent, ethylene glycol;    -   (ii) 20 ppm by weight to 99 weight percent of one or more        three-carbon diols and four-carbon diols selected from        1,2-propanediol, 1,3-propanediol, 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol; each based        on the total weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the ethylene glycol        and a minor amount of the three-carbon diols and/or four-carbon        diols contained in the mixed diol stream and an extract phase        comprising a major amount of the three-carbon diols and/or        four-carbon diols and a minor amount of the ethylene glycol        contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

A second embodiment of our invention is a process for recoveringpurified ethylene glycol from a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 20 weight percent to 99.5 weight percent, ethylene glycol;    -   (ii) 20 ppm by weight to 40 weight percent of one or more        three-carbon diols selected from 1,2-propanediol and        1,3-propanediol, and 20 ppm by weight to 30 weight percent of        one or more four-carbon diols selected from 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol; each based        on the total weight of diols, and    -   (iii) 5 weight percent to 35 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from 2-ethylhexanol,        cyclohexanol, n-hexanol, methyl isobutyl ketone, methyl        isopropyl ketone, methyl propyl ketone, diisobutyl ketone,        trioctylphosphine oxide, trihexylphosphine oxide, and mixtures        thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hexane, heptane, octane, decane, benzene, toluene, xylenes,        isoparaffinic mixed hydrocarbons having a boiling range between        90 and 325° C., methyl napththalenes, and mixtures thereof; to        form a raffinate phase comprising a major amount of the ethylene        glycol and a minor amount of the three-carbon diols and/or        four-carbon diols contained in the mixed diol stream and an        extract phase comprising a major amount of the three-carbon        diols and/or four-carbon diols and a minor amount of the        ethylene glycol contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

A third embodiment of our invention, is a process for recoveringpurified ethylene glycol from a mixed diol stream comprising ethyleneglycol and four-carbon diols, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 50 weight percent to 99.99 weight percent, ethylene glycol;    -   (ii) 0.01 weight percent to 50 weight percent of one or more        four-carbon diols selected from 1,2-butanediol, 1,3-butanediol,        1,4-butanediol, and 2,3-butanediol; each based on the total        weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the ethylene glycol        and a minor amount of the four-carbon diols contained in the        mixed diol stream and an extract phase comprising a major amount        of the four-carbon diols and a minor amount of the ethylene        glycol contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

Our process can also be used, for example, to separate glycols from thehydrogenolysis of glycerol. A fourth embodiment of our invention, is aprocess for recovering diols from a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 0.1 weight percent to 50 weight percent of one or more diols        selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol        1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and        2,3-butanediol;    -   (ii) 5 weight percent to 90 weight percent glycerol; and    -   (iii) 5 weight percent to 90 weight percent water; each based on        the total weight of the mixed diol stream with an extractant,        comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the glycerol and a        minor amount of the diols contained in the mixed diol stream and        an extract phase comprising a major amount of the diols and a        minor amount of the glycerol contained in the mixed diol stream;        and-   (B) separating the raffinate phase and the extract phase.

Our process can also be used, for example, to separate glycols from afermentation broth. A fifth embodiment of our invention, is a processfor recovering diols from a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 0.1 weight percent to 30 weight percent of ethylene glycol,        1,2-propanediol and 1,3-propanediol, 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol;    -   (ii) 5 to 50 weight percent glucose; and    -   (iii) 50 weight percent to 90 weight percent water; each based        on the total weight of the mixed diol stream, with an        extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the glucose and a        minor amount of the diols contained in the mixed diol stream and        an extract phase comprising a major amount of the diols and a        minor amount of the glucose contained in the mixed diol stream;        and-   (B) separating the raffinate phase and the extract phase.

A sixth embodiment of our invention, is a process for recoveringpurified three-carbon diols from a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 1 weight percent to 99.5 weight percent of one or more        three-carbon diols selected from 1,2-propanediol and        1,3-propanediol;    -   (ii) 20 ppm by weight to 99 weight percent of one or more        four-carbon diols selected from 1,2-butanediol, 1,3-butanediol,        1,4-butanediol, and 2,3-butanediol; each based on the total        weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the three-carbon        diols and a minor amount of the four-carbon diols contained in        the mixed diol stream and an extract phase comprising a major        amount of the four-carbon diols and a minor amount of the        three-carbon diols contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic flow diagram of one embodiment of the invention inwhich a mixed diol stream is subjected to forward extraction with ahydrophobic solvent to produce a raffinate containing ethylene glycolwhich is subject to purification via distillation and an extract whichis purified via distillation and recycled to the forward extractionstep.

FIG. 2 is a schematic flow diagram of another embodiment of theinvention in which the forward extraction zone is operated as afractional counter-current extraction, the hydrocarbon solvent in theextract is recovered via back extraction and recycled to the forwardextraction zone, and the three-carbon diols and four-carbon diols arerecovered in a distillation zone.

DETAILED DESCRIPTION

The present invention provides a method to separate two-, three-, andfour-carbon diols from a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 1 weight percent to 99.5 weight percent, ethylene glycol;    -   (ii) 20 ppm by weight to 99 weight percent of one or more        three-carbon diols and four-carbon diols selected from        1,2-propanediol, 1,3-propanediol, 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol; each based        on the total weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the ethylene glycol        and a minor amount of the three-carbon diols and/or four-carbon        diols contained in the mixed diol stream and an extract phase        comprising a major amount of the three-carbon diols and/or        four-carbon diols and a minor amount of the ethylene glycol        contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.” Accordingly,unless indicated to the contrary, the numerical parameters set forth inthe following specification and attached claims are approximations thatmay vary depending upon the desired properties sought to be obtained bythe present invention. At the very least, each numerical parametershould at least be construed in light of the number of reportedsignificant digits and by applying ordinary rounding techniques.Further, the ranges stated in this disclosure and the claims areintended to include the entire range specifically and not just theendpoint(s). For example, a range stated to be 0 to 10 is intended todisclose all whole numbers between 0 and 10 such as, for example 1, 2,3, 4, etc., all fractional numbers between 0 and 10, for example 1.5,2.3, 4.57, 6.1113, etc., and the endpoints 0 and 10. Also, a rangeassociated with chemical substituent groups such as, for example, “C₁ toC₅ hydrocarbons”, is intended to specifically include and disclose C₁and C₅ hydrocarbons as well as C₂, C₃, and C₄ hydrocarbons.

Also, it is to be understood that the mention of one or more processsteps does not preclude the presence of additional process steps beforeor after the combined recited steps or intervening process steps betweenthose steps expressly identified. Moreover, the lettering of processsteps or ingredients is a convenient means for identifying discreteactivities or ingredients and the recited lettering can be arranged inany sequence, unless otherwise indicated.

As used herein, the term “and/or,” when used in a list of two or moreitems, means that any one of the listed items can be employed by itself,or any combination of two or more of the listed items can be employed.For example, if a composition is described as containing components A,B, and/or C, the composition can contain A alone; B alone; C alone; Aand B in combination; A and C in combination; B and C in combination; orA, B, and C in combination.

As used herein, the term “feed” is intended to have its commonlyunderstood meaning in the liquid-liquid extraction art, which is thesolution that contains the materials to be extracted or separated. Inthe present invention, one example of a “feed” is a mixture comprised oftwo or more of ethylene glycol, 1,2-propanediol, 1,3-propanediol,1,2-butanediol, 2,3-butanediol, 1,3-butandediol, and 1,4-butanediol. Inthe present invention the term feed is synonymous with “mixed diolstream”. The term “extraction solvent,” as used herein, is intended tobe synonymous with the term “extractant” or “solvent” and is intended tomean the immiscible liquid that is used in the extraction process toextract materials or solutes from the feed. The term “extract” is theimmiscible liquid left from the extraction solvent after it has beencontacted with the feed. The term “raffinate” is intended to mean theliquid phase left from the feed after it has been contacted with theextraction solvent. The term “wash solvent” is understood to mean aliquid used to wash or enhance the purity of the raffinate or extractphase.

In the present invention, one example of an extraction solvent is analkanol containing 6 to 20 carbon atoms such as, for example,2-ethylhexanol. The term “alkanol”, as used herein, refers to an alkylcontaining 6 to 20 carbon atoms and at least one OH moiety. Otherexamples of extraction solvents are “ketones”, “esters”, “ethers”,“carboxylic acids”, and “hydrocarbons” which are terms well known tothose skilled in the art. The extraction solvent can also containtrialkylphosphine oxides. The term “trialkylphosphine oxides”, as usedherein, refers to phosphine oxides containing three alkyl moieties witha total of 18 to 48 carbon atoms including, but not limited to,trioctylphosphine oxide, isomeric 24-carbon phosphine oxides,trihexylphosphine oxide, and isomeric 18-carbon phosphine oxides. Theterm “hydrophobic solvent”, as used herein, refers to a solvent thatwill phase separate when mixed with the mixed diol stream and/or water.The term a “major amount”, as used herein, for example “a major amountof ethylene glycol contained in the mixed diol stream” refers to atleast 50 weight percent of the ethylene glycol contained in the mixeddiol stream. In a further example, when a raffinate phase comprises amajor amount of the ethylene glycol in the mixed diol stream, the weightof the ethylene glycol in the raffinate phase divide by the weight ofthe ethylene glycol in the mixed diol stream, on a weight percent basis,is greater than 50 weight percent. The term a “minor amount”, as usedherein, for example “a minor amount of ethylene glycol contained in themixed diol stream” refers to less than 50 weight percent of the ethyleneglycol contained in the mixed diol stream.

The process of the invention provides for the separation of a mixed diolstream. The term “mixed diol stream”, as used herein, is understood tomean a mixture comprising two or more of ethylene glycol,1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 2,3-butanediol,1,3-butandediol, and 1,4-butanediol. The terms “propanediols” and“three-carbon diols”, as used herein, are understood to mean a mixturecomprising one or more of 1,2-propanediol and 1,3-propanediol. The terms“butanediols” and “four-carbon diols”, as used herein, are understood tomean a mixture comprising one or more of 1,2-butanediol, 2,3-butanediol,1,3-butandediol, and 1,4-butanediol. The term “based on the total weightof diols”, as used herein, is understood to mean based on the summationof the amount of ethylene glycol, three-carbon diols, and four-carbondiols.

The mixed diol stream of the present invention can be produced by avariety of reaction methods including, but not limited to hydrogenationof glycolic acid, glycolate esters, oligomers of glycolic acid, estersof glycolic acid oligomers, or mixtures thereof, for example, asdisclosed in U.S. Pat. No. 7,615,671; hydrogenolysis of carbohydrates,such as sucrose, glucose, fructose, cellulose, sorbitol, or mixturesthereof, as disclosed, for example in U.S. Pat. Nos. 5,210,335,5,026,927, 6,291,725, and U.S. Pat. Appl. No. 2007123739; hydrogenolysisof glycerol, as exemplified by U.S. Pat. Nos. 5,276,181, 5,214,219, andU.S. Pat. Pub. No. 2007123739.

The mixed diol stream of the present invention may be derived from thereaction methods described above, but also may have undergone priorseparation methods to prepurify the mixed diol stream. For example areactor effluent from the hydrogenation of glycolate species may undergodistillation to remove low boilers, such as methanol, or high boilers,such as unreacted glycolic acid oligomers. Alternatively, at times itmay be advantageous to remove the lowest boiling, non-azeotrope formingpropanediols from a reactor effluent by single-feed fractionaldistillation, prior to the extraction steps of the present invention.

Our process comprises extracting a mixed diol stream that comprisesabout 1 to about 99.5 weight percent ethylene glycol and about 20 ppm to99 weight percent of one or more three-carbon and four-carbon diolsselected from 1,2-propanediol, 1,3-propanediol, 1,2-butanediol,2,3-butanediol, 1,3-butandediol, and 1,4-butanediol, each based on thetotal weight of diols; and 0 weight percent to 50 weight percent water,based on the total weight of diols and water. In another example, themixed diol stream, derived by the hydrogenolysis of sorbitol, comprisesabout 9 to about 23 weight percent butanediols(1,2-/1,3-/1,4-/2,3-butanediols), 32 to about 67 weight percent1,2-propanediol, and about 24 to about 59 weight percent ethyleneglycol. In another example, the mixed diol stream, derived by thehydrogenolysis of sorbitol glycerol, comprises about 40 to 90 weightpercent 1,2-propanediol, about 10 to about 60 weight percent ethyleneglycol, and about 0.1 to about 10 weight percent 1,2-butanediol. In afurther example, the mixed diol stream, derived from the hydrogenolysisof sucrose, comprises about 50 to about 65 weight percent1,2-propanediol, about 28 to about 45 weight percent ethylene glycol,and about 5 to about 7 weight percent 1,2-butanediol. In yet anotherexample, the mixed diol stream, derived from a prepurification step inwhich the 1,2-propanediol has been removed by ordinary single-feeddistillation, comprises about 50 to about 99.99 weight percent ethyleneglycol, and about 0.01 to about 50 weight percent butanediols.

In an aspect of the invention, the mixed diol stream comprises 1 weightpercent to 99.5 weight percent ethylene glycol, 1 weight percent to 90weight percent ethylene glycol; 1 weight percent to 80 weight percentethylene glycol, 1 weight percent to 70 weight percent ethylene glycol,10 weight percent to 99.5 weight percent ethylene glycol, 10 weightpercent to 90 weight percent ethylene glycol, 10 weight percent to 80weight percent ethylene glycol, 10 weight percent to 70 weight percentethylene glycol, 20 weight percent to 99.5 weight percent ethyleneglycol, 20 weight percent to 90 weight percent ethylene glycol, 20weight percent to 80 weight percent ethylene glycol, 20 weight percentto 70 weight percent ethylene glycol, or 20 weight percent to 60 weightpercent ethylene glycol; 20 ppm to 99.5 weight percent three-carbondiols and four-carbon diols, 20 ppm to 90 weight percent three-carbondiols and four-carbon diols, 20 ppm to 80 weight percent three-carbondiols and four-carbon diols, 20 ppm to 60 weight percent three-carbondiols and four-carbon diols, 20 ppm to 40 weight percent three-carbondiols and four-carbon diols, 20 ppm to 30 weight percent three-carbondiols and four-carbon diols, 20 ppm to 5 weight percent three-carbondiols and four-carbon diols, 20 ppm to 2 weight percent three-carbondiols and four-carbon diols, 0.1 weight percent to 99.5 weight percentthree-carbon diols and four-carbon diols, 0.1 weight percent to 90weight percent three-carbon diols and four-carbon diols, 0.1 weightpercent to 80 weight percent three-carbon diols and four-carbon diols,0.1 weight percent to 60 weight percent three-carbon diols andfour-carbon diols, 0.1 weight percent to 40 weight percent three-carbondiols and four-carbon diols, 0.1 weight percent to 30 weight percentthree-carbon diols and four-carbon diols, 0.1 weight percent to 5 weightpercent three-carbon diols and four-carbon diols, or 0.1 weight percentto 2 weight percent three-carbon diols and four-carbon diols, each basedon the total weight of diols.

In another aspect of the invention, the mixed diol stream comprises 1weight percent to 99.5 weight percent ethylene glycol, 1 weight percentto 90 weight percent ethylene glycol, 1 weight percent to 80 weightpercent ethylene glycol, 1 weight percent to 70 weight percent ethyleneglycol, 10 weight percent to 99.5 weight percent ethylene glycol, 10weight percent to 90 weight percent ethylene glycol, 10 weight percentto 80 weight percent ethylene glycol, 10 weight percent to 70 weightpercent ethylene glycol, 20 weight percent to 99.5 weight percentethylene glycol, 20 weight percent to 90 weight percent ethylene glycol,20 weight percent to 80 weight percent ethylene glycol, 20 weightpercent to 70 weight percent ethylene glycol, or 20 weight percent to 60weight percent ethylene glycol; 20 ppm to 60 weight percent three-carbondiols, 20 ppm to 40 weight percent three-carbon diols, 20 ppm to 30weight percent three-carbon diols, 20 ppm to 5 weight percentthree-carbon diols, 20 ppm to 2 weight percent three-carbon diols, 0.1weight percent to 60 weight percent three-carbon diols, 0.1 weightpercent to 40 weight percent three-carbon diols, 0.1 weight percent to30 weight percent three-carbon diols, 0.1 weight percent to 20 weightpercent three-carbon diols, 0.1 weight percent to 5 weight percentthree-carbon diols, 0.1 weight percent to 2 weight percent three-carbondiols; and 20 ppm to 60 weight percent four-carbon diols, 20 ppm to 40weight percent four-carbon diols, 20 ppm to 30 weight percentfour-carbon diols, 20 ppm to 20 weight percent four-carbon diols, 20 ppmto 5 weight percent four-carbon diols, 20 ppm to 2 weight percentfour-carbon diols, 0.1 weight percent to 60 weight percent four-carbondiols, 0.1 weight percent to 40 weight percent four-carbon diols, 0.1weight percent to 30 weight percent four-carbon diols, 0.1 weightpercent to 20 weight percent four-carbon diols, 0.1 weight percent to 5weight percent four-carbon diols, or 0.1 weight percent to 2 weightpercent four-carbon diols, each based on the total weight of diols.

In another aspect of the invention, the mixed diol stream comprises 5 to75 weight percent ethylene glycol, 30 weight percent to 95 weightpercent three-carbon diols, and 20 ppm to 10 weight percent four-carbondiols; or 10 weight percent to 60 weight percent ethylene glycol, 40weight percent to 90 weight percent 1,2-propanediol, and 0.1 weightpercent to 10 weight percent 1,2-butanediol, each based on the totalweight of diols.

In another aspect of the invention, the mixed diol stream comprises 20weight percent to 50 weight percent ethylene glycol, 45 weight percentto 70 weight percent three-carbon diols, and 1 weight percent to 10weight percent four-carbon diols; or 28 weight percent to 45 weightpercent ethylene glycol, 50 weight percent to 65 weight percent1,2-propanediol, and 5 weight percent to 7 weight percent1,2-butanediol, each based on the total weight of diols.

In another aspect of the invention, the mixed diol stream comprises 10weight percent to 60 weight percent ethylene glycol, 25 weight percentto 75 weight percent three-carbon diols, and 5 weight percent to 25weight percent four-carbon diols; or 20 weight percent to 50 weightpercent ethylene glycol, 30 weight percent to 70 weight percent1,2-propanediol, and 5 weight percent to 25 weight percent four-carbondiols, each based on the total weight of diols.

In another aspect of the invention, the mixed diol stream comprises 40weight percent to 99.99 weight percent ethylene glycol, 40 weightpercent to 99 weight percent ethylene glycol, 40 weight percent to 90weight percent ethylene glycol, 40 weight percent to 80 weight percentethylene glycol, 50 weight percent to 99.99 weight percent ethyleneglycol, 50 weight percent to 99 weight percent ethylene glycol, 50weight percent to 90 weight percent ethylene glycol, or 50 weightpercent to 80 weight percent ethylene glycol; and 0.001 weight percentto 60 weight percent four-carbon diols, 0.001 weight percent to 50weight percent four-carbon diols, 0.001 weight percent to 40 weightpercent four-carbon diols, 0.001 weight percent to 30 weight percentfour-carbon diols, 0.001 weight percent to 20 weight percent four-carbondiols, 0.01 weight percent to 60 weight percent four-carbon diols, 0.01weight percent to 50 weight percent four-carbon diols, 0.01 weightpercent to 40 weight percent four-carbon diols, 0.01 weight percent to30 weight percent four-carbon diols, 0.01 weight percent to 20 weightpercent four-carbon diols, 1 weight percent to 60 weight percentfour-carbon diols, 1 weight percent to 50 weight percent four-carbondiols, 1 weight percent to 40 weight percent four-carbon diols, 1 weightpercent to 30 weight percent four-carbon diols, or 1 weight percent to20 weight percent four-carbon diols, each based on the total weight ofdiols.

In another aspect of the invention, the mixed diol stream comprises 1weight percent to 99.99 weight percent three-carbon diols, 1 weightpercent to 99 weight percent three-carbon diols, 1 weight percent to 90weight percent three-carbon diols, 1 weight percent to 80 weight percentthree-carbon diols, 10 weight percent to 99.99 weight percentthree-carbon diols, 10 weight percent to 99 weight percent three-carbondiols, 10 weight percent to 90 weight percent three-carbon diols, 10weight percent to 80 weight percent three-carbon diols; and 20 ppm to99.99 weight percent four-carbon diols, 20 ppm to 99 weight percentfour-carbon diols, 20 ppm to 90 weight percent four-carbon diols, 20 ppmto 80 weight percent four-carbon diols, 0.001 weight percent to 99.99weight percent four-carbon diols, 0.001 weight percent to 99 weightpercent four-carbon diols, 0.001 weight percent to 90 weight percentfour-carbon diols, 0.001 weight percent to 80 weight percent four-carbondiols, 0.01 weight percent to 99 weight percent four-carbon diols, 0.01weight percent to 90 weight percent four-carbon diols, 0.01 weightpercent to 80 weight percent four-carbon diols, 0.01 weight percent to70 weight percent four-carbon diols, 1 weight percent to 99 weightpercent four-carbon diols, 1 weight percent to 90 weight percentfour-carbon diols, 1 weight percent to 80 weight percent four-carbondiols, or 1 weight percent to 70 weight percent four-carbon diols, eachbased on the total weight of diols.

In another aspect of the invention, any of the mixed diol streams abovecan further comprise water. The water can be present in the mixed diolstream as received or may be added to the mixed diol stream. The amountof water, based on the total amount of diols and water, for example, canrange from 0.5 weight percent to 80 weight percent water, 0.5 weightpercent to 50 weight percent water, 0.5 weight percent to 40 weightpercent water, 0.5 weight percent to 25 weight percent water, 1 weightpercent to 80 weight percent water, 1 weight percent to 50 weightpercent water, 1 weight percent to 40 weight percent water, 1 weightpercent to 25 weight percent water, 5 weight percent to 80 weightpercent water, 5 weight percent to 60 weight percent water, 5 weightpercent to 50 weight percent water, 5 weight percent to 40 weightpercent water, 5 weight percent to 35 weight percent water, 5 weightpercent to 25 weight percent water, 5 weight percent to 15 weightpercent water, 10 weight percent to 50 weight percent water, or 10weight percent to 25 weight percent water.

The mixed diol stream is contacted with an extractant that comprises atleast one hydrophobic solvent selected from alkanols having from 6 to 20carbon atoms, ketones having from 5 to 20 carbon atoms, esters havingfrom 5 to 20 carbon atoms, ethers having from 5 to 20 carbon atoms,alkyl carbonate esters having from 3 to 20 carbon atoms,trialkylphosphine oxides having from 18 to 48 carbon atoms, and mixturesthereof. Some representative examples of hydrophobic solvents include,but are not limited to, 2-ethylhexanol, n-heptanol, n-hexanol,cyclohexanol, 4-methyl-2-pentanol, n-octanol, n-nonanol, n-decanol,tetradecanol isomers, 3-methyl-2-butanone, methyl isobutyl ketone (alsoknown as 4-methyl-2-pentanone), methyl isopropyl ketone, methyl propylketone, diisobutyl ketone, isobutylisobutyrate, ethyl acetate, n-butylacetate, isobutylacetate, isopropylacetate, n-propyl acetate,diispropylether, dibutylether, tertiary-amyl methyl ether,tertiary-butyl methyl ether, trioctylphosphine oxide and isomeric24-carbon phosphine oxides, trihexylphosphine oxide and isomeric18-carbon phosphine oxides, and mixtures thereof. For example, in oneaspect of our inventive process, the hydrophobic extraction solventcomprises 2-ethylhexanol. In another aspect of our inventive process,the hydrophobic extraction solvent comprises trioctylphosphine oxide,trihexylphosphine oxide, and/or isomeric 24-carbon and 18-carbonphosphine oxides, as exemplified by the CYANEX® solvents, such asCYANEX® 923 and CYANEX®921 (available from Cytec Industries, Inc., 5Garret Mountain Plaza, Woodland Park, N.J.). In one aspect of theinvention, the hydrophobic solvent may be selected from 2-ethylhexanol,cyclohexanol, n-hexanol, methyl isobutyl ketone, methyl isopropylketone, methyl propyl ketone, diisobutyl ketone, propylene carbonate,trioctylphosphine oxide, trihexylphosphine oxide, and mixtures thereof.The hydrophobic solvent may be selected from 2-ethylhexanol,cyclohexanol, n-hexanol, methyl isobutyl ketone, methyl isopropylketone, methyl propyl ketone, diisobutyl ketone, trioctylphosphineoxide, trihexylphosphine oxide, and mixtures thereof. The hydrophobicsolvent may be selected from 2-ethylhexanol, cyclohexanol,trioctylphosphine oxide, trihexylphosphine oxide and mixtures thereof.

Mixtures of one or more different hydrophobic solvents may be employedif desired. The amount of hydrophobic extraction solvent employed is notcritical to the subject invention and need only be that amountsufficient to extract the one or more diols from the mixed diol streamfor any given process and to ensure the formation of two immiscibleliquid phases throughout the extraction zones. In general, the amount ofhydrophobic extraction solvent employed may range from about 10 percentby weight up to about 500 percent by weight or more based on the totalweight of the mixed diol stream. The use of the high percentage ofhydrophobic extraction solvent may be necessary, for example, when thereare only a limited number of stages in a counter-current extractionprocess.

The hydrophobic solvent of the extractant may further comprise a secondmodifying hydrophobic solvent to modify the physical and transportproperties of the extractant. The second modifying hydrophobic solventcan be selected from hydrocarbons having from 5 to 20 carbon atoms. Somerepresentative examples of hydrocarbons include hexane, heptane, octane,decane, benzene, toluene, xylenes, methyl napththalenes, and mixturesthereof. For example, the hydrocarbon may comprise isoparaffinic mixedhydrocarbons having boiling ranges between about 90 and about 325° C.,as exemplified by the ISOPAR™ solvents (available from Exxon ChemicalCo., Houston, Tex.), such as ISOPAR C (boiling point range of 98 to 104°C.), ISOPAR E (boiling point range of 118 to 137° C.), ISOPAR G (boilingpoint range of 160 to 176° C.), ISOPAR H (boiling point range of 178 to188° C.), ISOPAR K (boiling point range of 178 to 197° C.), ISOPAR L(boiling point range of 189 to 207° C.), ISOPAR M (boiling point rangeof 223 to 254° C.), and ISOPAR V (boiling point range of 273 to 312°C.).

In some aspects of the invention, the hydrocarbon can be lower boilingthan the other hydrophobic solvent components and, thus, can be readilyseparated from the other components by distillation. If more than onehydrophobic solvent is used as the extractant, these solvents may or maynot form azeotropic mixtures under distillation conditions employed.

The relative amounts of the hydrophobic solvent and the second modifyinghydrophobic solvent can be varied to optimize the extraction. In anaspect of the invention, the extractant comprises 50 weight percent to100 weight percent of the hydrophobic solvent and 0 weight percent to 50weight percent of the second, modifying hydrophobic solvent; 50 weightpercent to 95 weight percent of the hydrophobic solvent and 5 weightpercent to 50 weight percent of the second, modifying hydrophobicsolvent; 60 weight percent to 95 weight percent of the hydrophobicsolvent and 5 weight percent to 40 weight percent of the second,modifying hydrophobic solvent, or 70 weight percent to 90 weight percentof the hydrophobic solvent and 10 weight percent to 30 weight percent ofthe second, modifying hydrophobic solvent.

An example, hydrophobic solvent mixture comprises an alcohol selectedfrom cyclohexanol, n-hexanol, n-octanol, 4-methyl-2-pentanol,2-ethylhexanol; and a hydrocarbon selected from one or more of C9 to C11alkanes such as n-nonane, n-decane, n-undecane, ISOPAR G (boiling pointrange of 160 to 176° C.), ISOPAR H (boiling point range of 178 to 188°C.), ISOPAR K (boiling point range of 178 to 197° C.), ISOPAR L (boilingpoint range of 189 to 207° C.), or mixtures thereof. Another examplehydrophobic solvent mixture comprises isomeric trioctylphosphine oxide,isomeric trihexylphosphine oxide, and mixtures thereof, and ahydrocarbon selected from one or more of C9 to C11 alkanes such asn-nonane, n-decane, n-undecane, ISOPAR G (boiling point range of 160 to176° C.), ISOPAR H (boiling point range of 178 to 188° C.), ISOPAR K(boiling point range of 178 to 197° C.), ISOPAR L (boiling point rangeof 189 to 207° C.), or mixtures thereof.

If an alcohol is used as the hydrophobic solvent of the extractant, thenat least 5 weight percent water, based on total weight of mixed diolstream and water, must be introduced into the first extraction zone toensure two phases form in the extractor. In another aspect, wherein analcohol is used as the hydrophobic solvent, the amount of waterintroduced is 5 to 60 weight percent, based on total weight of mixeddiol stream and water. In yet another aspect, wherein an alcohol is usedas the hydrophobic solvent, the amount of water introduced is 10 to 50weight percent based on total weight of mixed diol stream and water.

As noted above, the optional water introduced into the first extractioncan be present in the mixed diol stream as received. The optional watercan be introduced to the extraction process at one or more differentlocations. In one aspect for example, the optional water can be added tothe mixed diol stream. In another aspect, the water can be introducedinto the extractor as a separate feed. In yet another aspect, theextractor may be operated as a fractional extractor with one or morewater feed points.

The process of the present invention forms a raffinate phase comprisinga major amount of ethylene glycol and a minor amount of three-carbondiols and/or four-carbon diols contained in the mixed diol stream. In anaspect of the invention, greater than 95 weight percent of the ethyleneglycol in the mixed diol stream is recovered in the raffinate phase. Inanother aspect, greater than 98 weight percent, greater than 99 weightpercent, greater than 99.5 weight percent, or greater than 99.99 weightpercent of the ethylene glycol in the mixed diol stream is recovered inthe raffinate phase.

The process of the present invention forms an extract phase comprising amajor amount of the three-carbon diols and/or the four-carbon diols anda minor amount of the ethylene glycol. In an aspect of the inventiongreater than 60 weight percent of the four-carbon diols in the mixeddiol stream is recovered in the extract phase. In another aspect,greater than 70 weight percent, greater than 80 weight percent, greaterthan 90 weight percent, greater than 95 weight percent, greater than 98weight percent, or greater than 99 weight percent of the four-carbondiols in the mixed diol stream is recovered in the extract phase.

The raffinate phase can be concentrated in ethylene glycol. Theconcentration of ethylene glycol, based on the total weight of diols inthe raffinate phase can be greater than 95 weight percent, or greaterthan 98 weight percent, or greater than 99 weight percent, or greaterthan 99.9 weight percent, or greater than 99.99 weight percent. Theconcentration of three-carbon diols and four-carbon diols, based on thetotal weight of diols in the raffinate phase, can be less than 5 weightpercent, less than 1 weight percent, less than 0.5 weight percent, lessthan 1000 ppm on a weight basis, less than 500 ppm on a weight basis,less than 100 ppm on a weight basis, or less than 50 ppm on a weightbasis.

The extraction of the mixed diol stream can be carried out by any meansknown in the art to intimately contact two immiscible liquid phases andto separate the resulting phases after the extraction procedure. Forexample, the extraction can be carried out using columns, centrifuges,mixer-settlers, and miscellaneous devices. Some representative examplesof extractors include unagitated columns (e.g., spray, baffle tray andpacked, perforated plate), agitated columns (e.g., pulsed, rotaryagitated, and reciprocating plate), mixer-settlers (e.g., pump-settler,static mixer-settler, and agitated mixer-settler), centrifugalextractors (e.g., those produced by Robatel, Luwesta, deLaval, DorrOliver, Bird, CINC, and Podbielniak), and other miscellaneous extractors(e.g., emulsion phase contactor, electrically enhanced extractors, andmembrane extractors). A description of these devices can be found in the“Handbook of Solvent Extraction”, Krieger Publishing Company, Malabar,Fla., 1991, pp. 275-501. The various types of extractors may be usedalone or in any combination.

The extraction may be conducted in one or more stages. The number ofextraction stages can be selected in consideration of capital costs,achieving high extraction efficiency, ease of operability, and thestability of the starting materials and mixed diol stream to theextraction conditions. The extraction also can be conducted in a batchor continuous mode of operation. In a continuous mode, the extractionmay be carried out in a co-current, a counter-current manner, or as afractional extraction in which multiple solvents and/or solvent feedpoints are used to help facilitate the separation. The extractionprocess also can be conducted in a plurality of separation zones thatcan be in series or in parallel.

The extraction typically can be carried out at a temperature of about 10to about 120° C. For example, the extraction can be conducted at atemperature of about 30 to about 80° C. The desired temperature rangemay be constrained further by the boiling point of the extractantcomponents or water. Generally, it is undesirable to operate theextraction under conditions where the extractant boils. In one aspect,the extractor can be operated to establish a temperature gradient acrossthe extractor in order to improve the mass transfer kinetics ordecantation rates. In another aspect, the extractor may be operatedunder sufficient pressure to prevent boiling.

In an aspect of the invention, the mixed diol stream is extracted in acontinuous counter-current extractor. The extractant is fed to theextractor at a location lower than the feed location of the mixed diolstream. The extractant moves up the counter-current extractor to form anextract phase exiting the top of the extractor and comprising a majoramount of the three-carbon diols and/or the four-carbon diols and aminor amount of the ethylene glycol contained in the mixed diol stream.The mixed diol stream moves down the counter-current extractor to formthe raffinate phase exiting the bottom of the extractor and comprising amajor amount of the ethylene glycol and a minor amount of thethree-carbon diols and/or the four-carbon diols contained in the mixeddiol stream. In an aspect of the invention the feed ratio of theextractant to the mixed diol stream ranges from 0.5:1 to 20:1, or 1:1 to10:1, or 1:1 to 5:1.

The mixed diol stream and extractant can be contacted by fractionalextraction methods such as, for example, by fractional counter-currentextraction. As used herein, the term “fractional counter-currentextraction” is intended to include, but is not limited to, a method forseparating a feed stream, e.g., reaction product fluid, containing twoor more substances by charging the feed stream to a counter-currentextraction process between the points where two immiscible solvents arecharged to the extraction process. The two immiscible solvents should beimmiscible over the entire temperature range of the extraction process.This method is sometimes referred to as “double solvent extraction.”Fractional counter-current extraction can involve the use of a cascadeof stages, extracting solvents and solution to be extracted entering atopposite ends of the cascade with the feed phase and hydrophobicextractant phase flowing counter-currently. Some example fractionalcounter-current extraction configurations may be found in Treybal,Liquid Extraction, 2nd Edition, McGraw-Hill Book Company, New York.1963, pp. 275-276.

In an aspect of the invention, the mixed diol stream is extracted in acontinuous fractional counter-current extractor. The extractant is fedto the extractor at a location lower than the feed location of the mixeddiol stream. A hydrophilic solvent is fed to the extractor at a locationhigher than the mixed diol stream. In an aspect of the invention thefeed ratio of the extractant to the mixed diol stream ranges from 0.5:1to 20:1, or 1:1 to 10:1, or 1:1 to 5:1 and the feed ratio of thehydrophilic solvent to the mixed diol stream ranges from 0.05:1 to 2:1,or 0.1:1 to 1.5:1, or 0.1:1 to 0.8:1. The hydrophilic solvent maycomprise water.

The extraction of the mixed diol stream produces a raffinate phasecomprising a major amount of the lowest-carbon-number diols and a minoramount of the highest-carbon-number diols contained in the mixed diolstream and an extract phase comprising a major amount of thehighest-carbon-number diols and a minor amount of thelowest-carbon-number diols contained in the mixed diol stream. Theraffinate phase and the extract phase may be separated by any phaseseparation technology known in the art. The phase separation techniquescan be accomplished in the extractor or in a separate liquid-liquidseparation device. Suitable liquid-liquid separation devices include,but are not limited to, coalescers, cyclones and centrifuges. Typicalequipment that can be used for liquid-liquid phase separation devicesare described in the Handbook of Separation process Technology, ISBN0-471-89558-X, John Wiley & Sons, Inc., 1987.

Removal of the extracted diols and recycle of the hydrophobic extractantis another aspect of the instant invention. A majority of thethree-carbon diols and four-carbon diols can be removed from the extractphase to form a lean hydrophobic solvent. The lean hydrophobic solventcan be recycled whereby the extractant of step (B) comprises at least aportion of the lean hydrophobic solvent. The removal and recycle processmay entail extraction, distillation or a combination of these unitoperations. When extraction is chosen to produce the lean solvent, thestep of extracting the mixed diol stream is called a forward extractionand the step of extracting the hydrophobic solvent extract exiting theforward extraction is called a back extraction. When distillation ischosen as the diol recovery method, the hydrophobic extractant ispreferentially selected such that at least one component of theextractant forms a minimum boiling azeotrope with the diol componentscontained in the extract phase. Most preferably, the minimum-boilingazeotrope formed with the diol components is heterogeneous in nature,i.e., forms two liquid phases upon condensation.

In one aspect of the invention, diols contained in the extract phase arerecovered by distillation wherein the diol-laden extract phase is fed toa distillation column, and the diols are removed overhead as theminimum-boiling azeotropes between at least one hydrophobic extractantcomponent and the diol components to form a distillate product; and thebottoms product comprises a majority of the hydrophobic extractantcomponents.

Examples of hydrophobic extractant components that form azeotropes withtwo-, three-, and four-carbon diols are hydrocarbons containing seven tofourteen carbon atoms such as toluene, p-xylene, o-xylene, m-xylene,ethylbenzene, 1,3,5-trimethylbenzene, 1,2,4-trimethylbenzene,isopropylbenzene, heptane, n-octane, 2,2-4-trimethyl-pentane, n-nonane,n-decane, n-undecane, and mixtures thereof.

Additional exemplary hydrophobic extractant components that formheterogeneous minimum-boiling azeotropes with ethylene glycol,butanediols, and propanediols are normal- and iso-paraffinichydrocarbons containing six to fourteen carbon atoms and mixturesthereof, most preferably normal- and iso-paraffinic hydrocarbonscontaining nine to eleven carbon atoms and mixtures thereof. Forexample, preferable paraffinic hydrocarbons are n-octane,2,2-4-trimethyl-pentane, n-nonane, n-decane, n-undecane, and mixturesthereof. The azeotrope-forming component also may comprise isoparaffinicmixed hydrocarbons having boiling ranges between about 100 and about225° C., as exemplified by the ISOPAR™ solvents, such as Isopar E(boiling point range of 118 to 137° C.), ISOPAR G (boiling point rangeof 160 to 176° C.), ISOPAR H (boiling point range of 178 to 188° C.),ISOPAR K (boiling point range of 178 to 197° C.), ISOPAR L (boilingpoint range of 189 to 207° C.).

Optionally, one or more hydrocarbons may be added to the distillationfeed stream or provided as reflux to the distillation column to enhancethe azeotropic separation of the diols. It is advantageous that theminimum boiling azeotropes formed between the diols and the hydrophobicextractant component have a high diol content. Examples of high diolcontent azeotropes include those with greater than 5 weight percent diolor greater than 15 weight percent diol. Examples of hydrophobic solventand diol azeotropes are given in the table below where pure componentboiling points (NBP), azeotrope boiling points (Azeo BP), and weightpercent of alkane in the azeotrope are given for ethylene glycol (EG),butanediol (DBO) and propanediol (PDO) with nonane, decane, undecane,and 2-ethylhexanol (2-EH) as the solvent:

NBP, C EG BDO PDO NBP, C 197.1 196.5 187.7 Azeo BP, C nonane 150.8 144.3145.3 143.2 Decane 174.3 160.8 162.2 158.7 undecane 195.9 172.7 174.2169.3 2-EH 184.6 177.1 183.2 178.4 wt % alkane in azeo nonane 91.7%89.3% 91.2% Decane 84.2% 80.0% 77.6% undecane 75.1% 68.6% 60.8% 2-EH75.0% 82.5% 67.8%

If the diol and the azeotroping agent do not form two liquid phases,i.e., do not form a heterogeneous azeotrope, then water may optionallybe added to the distillate product to assist in the generation of twoliquid phases. Water may be added in an amount equal to 10 to 100percent by weight of the distillate product. When water is added, thediols will partition preferentially into a water-rich phase. The organicphase, largely free of diols may be returned to the distillation columnas reflux. The water-rich phase may be further treated to removehydrophobic solvent components by steam distillation wherein live steamis added to the column, or by distillation of water-hydrophobic solventazeotropes as an overhead product.

As noted above, when extraction is chosen to produce the lean solvent,the step of extracting the mixed diol stream is called a forwardextraction and the step of extracting the hydrophobic solvent extractphase which exits the forward extraction is called a back extraction.Thus, in another aspect of the invention, diol components can be removedfrom the extract phase into water and a lean solvent recovered via aback extraction process. Our process also comprises extracting theextract phase from step (B) with a second extractant comprising water toform a second extract phase comprising a major amount of the diolcomponents contained in the extract phase from step (B) and a secondraffinate phase (i.e., lean solvent) comprising a minor amount of thediol composition contained in the extract phase from step (B).Typically, the concentration of diol in the second extract phase can beabout 1 to about 50 percent by weight or, in another example, about 5 toabout 20 percent by weight.

The second extract phase can be passed to a process for recovery ofhydrophobic solvent components, for example by distillation or steamstripping. The second raffinate phase can be recycled to the firstextraction by combining the second raffinate phase with the firstextractant. The second raffinate phase can be distilled prior to recycleto produce a hydrophobic solvent distillate that is subsequentlycombined with the extractant of step (A).

The weight ratio of the second extractant to the first extract phasefrom step (B) of our inventive process is about 0.05:1 to about 5:1.Further examples of weight ratios of the second extractant to the firstextract phase are about 0.1:1 to 3:1 and about 0.1:1 to about 2:1.

The back extraction process can be conducted at a temperature of about10 to about 120° C. For example, in one aspect of the invention, theback extraction step of the invention is carried out at a temperature ofabout 30 to about 80° C.

The back extraction process can be carried out by any extraction meansknown in the art to intimately contact two immiscible liquid phases andto separate the resulting phases after the extraction procedure. Forexample, the back extraction can be carried out using columns,centrifuges, mixer-settlers, and miscellaneous devices. The varioustypes of extractors may be used alone or in any combination.

The back extraction may be conducted in one or more stages. The backextraction also can be conducted in a batch or continuous fashion. In acontinuous mode, the back extraction may be carried out in a co-current,a counter-current manner, or as a fractional extraction in whichmultiple solvents and/or solvent feed points are used to help facilitatethe separation. Further, the back extraction process of this inventioncan be conducted in a plurality of separation zones in series or inparallel.

Optionally, an additional hydrophobic solvent may be employed to modifythe physical and transport properties of the hydrophobic extract phaseprior to introduction into the back extraction process. This additionalhydrophobic solvent can be the same as the optional, second hydrophobicsolvent employed in the forward extraction zone. The optional additionof the second hydrophobic extraction solvent can be used to remove anyunwanted relatively hydrophobic components from the hydrophilic extractphase of the back extractor zone. In one embodiment, the secondhydrophobic extraction solvent is not required, and the back extractoris operated as a traditional extractor instead of as a fractionalextractor.

Alternatively, the back extraction process may be operated in afractional extraction mode with the additional second hydrophobicsolvent added at a feed point closer to the end of the extractor wherethe back extraction raffinate stream exits than the feed point of thehydrophobic extract phase from the forward extraction zone. The massfeed ratio of the additional second hydrophobic solvent to thehydrophobic extract phase from the forward extraction zone can bebetween 0:1 and 1.5:1 or between 0.05:1 and 0.45:1.

The forward extraction of the mixed diol stream also produces araffinate phase which, in addition to ethylene glycol, can comprisethree-carbon diols, four-carbon diols, water, and hydrophobic solvent.The raffinate phase can be further processed to recover a high-purityethylene glycol product. For example, the raffinate phase can be fed toa distillation column where water and hydrophobic solvent can beseparated from the diols. The hydrophobic solvent can be furtherprocessed and/or recycled to the extractor.

A further embodiment of our invention is a process for recoveringpurified ethylene glycol from a mixed diol stream, comprising

-   -   (A) extracting the mixed diol stream, comprising        -   (i) 20 weight percent to 99.5 weight percent, ethylene            glycol;        -   (ii) 20 ppm by weight to 40 weight percent of one or more            three-carbon diols selected from 1,2-propanediol and            1,3-propanediol, and 20 ppm by weight to 30 weight percent            of one or more four-carbon diols selected from            1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and            2,3-butanediol; each based on the total weight of diols, and        -   (iii) 5 weight percent to 35 weight percent water, based on            the total weight of diols and water, with an extractant,            comprising        -   (i) a hydrophobic solvent selected from 2-ethylhexanol,            cyclohexanol, n-hexanol, methyl isobutyl ketone, methyl            isopropyl ketone, methyl propyl ketone, diisobutyl ketone,            trioctylphosphine oxide, trihexylphosphine oxide, and            mixtures thereof; and        -   (ii) optionally, a second modifying hydrophobic solvent            selected from hexane, heptane, octane, decane, benzene,            toluene, xylenes, isoparaffinic mixed hydrocarbons having a            boiling range between 90 and 325° C., methyl napththalenes,            and mixtures thereof; to form a raffinate phase comprising a            major amount of the ethylene glycol and a minor amount of            the three-carbon diols and/or four-carbon diols contained in            the mixed diol stream and an extract phase comprising a            major amount of the three-carbon diols and/or four-carbon            diols and a minor amount of the ethylene glycol contained in            the mixed diol stream; and    -   (B) separating the raffinate phase and the extract phase.

The various aspects of mixed diol stream composition, water content,hydrophobic solvent, second modifying hydrophobic solvent, weightpercent of hydrophobic solvent and second modifying hydrophobic solventin the extractant, recovery of ethylene glycol, three-carbon and/orfour-carbon diols in the mixed diol stream to the raffinate phase,extraction process, extract phase clean-up and lean solvent recycle, andrecovery of high-purity ethylene glycol from the raffinate phasediscussed above apply to the present embodiment. For example, the mixeddiol stream can comprise 20 weight percent to 99.5 weight percentethylene glycol, 20 weight percent to 90 weight percent ethylene glycol,20 weight percent to 80 weight percent ethylene glycol, 20 weightpercent to 70 weight percent ethylene glycol, or 20 weight percent to 60weight percent ethylene glycol; 20 ppm to 40 weight percent three-carbondiols, 20 ppm to 30 weight percent three-carbon diols, 0.1 weightpercent to 40 weight percent three-carbon diols, 0.1 weight percent to30 weight percent three-carbon diols, or 0.1 weight percent to 20 weightpercent three-carbon diols; and 20 ppm to 40 weight percent four-carbondiols, 20 ppm to 30 weight percent four-carbon diols, 20 ppm to 20weight percent four-carbon diols, 0.1 weight percent to 40 weightpercent four-carbon diols, 0.1 weight percent to 30 weight percentfour-carbon diols, or 0.1 weight percent to 20 weight percentfour-carbon diols, each based on the total weight of diols. The amountof water in the mixed diol stream, based on the total weight of diolsand water, can range from 5 weight percent to 35 weight percent water, 5weight percent to 25 weight percent water, 5 weight percent to 15 weightpercent water, 10 weight percent to 35 weight percent water, or 10weight percent to 25 weight percent water.

The extractant can comprises at least one hydrophobic solvent selectedfrom 2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutyl ketone,methyl isopropyl ketone, methyl propyl ketone, and diisobutyl ketone,trioctylphosphine oxide, trihexylphosphine oxide, and mixtures thereof.In another aspect, the hydrophobic solvent can be selected from2-ethylhexanol, cyclohexanol, trioctylphosphine oxide, trihexylphosphineoxide, and mixtures thereof. The optional, second modifying hydrophobicsolvent can be selected from hydrocarbons having from 5 to 20 atoms. Thesecond, modifying hydrophobic solvent can be selected from hexane,heptane, octane, decane, benzene, toluene, xylenes, methylnapththalenes, isoparaffinic mixed hydrocarbons having boiling rangesbetween about 90 and about 325° C., and mixtures thereof.

A third embodiment of our invention, is a process for recoveringpurified ethylene glycol from a mixed diol stream comprising ethyleneglycol and four-carbon diols, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 50 weight percent to 99.99 weight percent, ethylene glycol;    -   (ii) 0.01 weight percent to 50 weight percent of one or more        four-carbon diols selected from 1,2-butanediol, 1,3-butanediol,        1,4 butanediol, and 2,3-butanediol; each based on the total        weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the ethylene glycol        and a minor amount of the four-carbon diols contained in the        mixed diol stream and an extract phase comprising a major amount        of the four-carbon diols and a minor amount of the ethylene        glycol contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

The various aspects of mixed diol stream composition, water content,hydrophobic solvent, second modifying hydrophobic solvent, weightpercent of hydrophobic solvent and second modifying hydrophobic solventin the extractant, recovery of ethylene glycol and/or four-carbon diolsin the mixed diol stream to the raffinate phase, extraction process,extract phase clean-up and lean solvent recycle, and recovery ofhigh-purity ethylene glycol from the raffinate phase discussed aboveapply to the present embodiment. For example, the mixed diol stream cancomprise 50 weight percent to 99.99 weight percent ethylene glycol, 50weight percent to 99 weight percent ethylene glycol, 50 weight percentto 95 weight percent ethylene glycol, 50 weight percent to 90 weightpercent ethylene glycol, 50 weight percent to 80 weight percent ethyleneglycol, 60 weight percent to 99.99 weight percent ethylene glycol, 60weight percent to 99 weight percent ethylene glycol, 60 weight percentto 95 weight percent ethylene glycol, 60 weight percent to 90 weightpercent ethylene glycol, 60 weight percent to 80 weight percent ethyleneglycol, 70 weight percent to 99.99 weight percent ethylene glycol, 70weight percent to 99 weight percent ethylene glycol, 70 weight percentto 95 weight percent ethylene glycol, 70 weight percent to 90 weightpercent ethylene glycol, or 70 weight percent to 80 weight percentethylene glycol; and 0.01 weight percent to 50 weight percentfour-carbon diols, 0.01 weight percent to 40 weight percent four-carbondiols, 0.01 weight percent to 30 weight percent four-carbon diols, 0.01weight percent to 20 weight percent four-carbon diols, 0.01 weightpercent to 5 weight percent four-carbon diols, 0.01 weight percent to 2weight percent four-carbon diols, 1 weight percent to 50 weight percentfour-carbon diols, 1 weight percent to 40 weight percent four-carbondiols, 1 weight percent to 30 weight percent four-carbon diols, 1 weightpercent to 20 weight percent four-carbon diols, 1 weight percent to 5weight percent four-carbon diols, 1 weight percent to 2 weight percentfour-carbon diols, 5 weight percent to 50 weight percent four-carbondiols, 5 weight percent to 40 weight percent four-carbon diols, 5 weightpercent to 30 weight percent four-carbon diols, or 5 weight percent to20 weight percent four-carbon diols.

Our process can also be used, for example, to separate glycols from thehydrogenolysis of glycerol. A fourth embodiment of our invention, is aprocess for recovering diols from a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 0.1 weight percent to 50 weight percent of one or more diols        selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol        1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and        2,3-butanediol;    -   (ii) 5 weight percent to 90 weight percent glycerol; and    -   (iii) 5 weight percent to 90 weight percent water; each based on        the total weight of the mixed diol stream with an extractant,        comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the glycerol and a        minor amount of the diols contained in the mixed diol stream and        an extract phase comprising a major amount of the diols and a        minor amount of the glycerol contained in the mixed diol stream;        and-   (B) separating the raffinate phase and the extract phase.

The various aspects of hydrophobic solvent, second modifying hydrophobicsolvent, weight percent of hydrophobic solvent and second modifyinghydrophobic solvent in the extractant apply to the present embodiment.

For example, the mixed diol stream can comprise 0.1 weight percent to 50weight percent ethylene glycol, 5 weight percent to 50 weight percentethylene glycol, 10 weight percent to 40 weight percent ethylene glycol,10 weight percent to 30 weight percent ethylene glycol, or 20 weightpercent to 40 weight percent ethylene glycol; 0.1 weight percent to 40weight percent three-carbon diols, 0.1 weight percent to 30 weightpercent three-carbon diols, 1 weight percent to 40 weight percentthree-carbon diols, 1 weight percent to 30 weight percent three-carbondiols, or 1 weight percent to 20 weight percent three-carbon diols; and0.1 weight percent to 40 weight percent four-carbon diols, 0.1 weightpercent to 30 weight percent four-carbon diols, 0.1 weight percent to 20weight percent four-carbon diols, 1 weight percent to 40 weight percentfour-carbon diols, 1 weight percent to 30 weight percent four-carbondiols, or 1 weight percent to 20 weight percent four-carbon diols, eachbased on the total weight of the mixed diol stream.

The amount of glycerol in the mixed diol stream, based on the totalweight of the mixed diol stream, can range from 5 weight percent to 90weight percent, 5 weight percent to 70 weight percent, 5 weight percentto 50 weight percent, 5 weight percent to 25 weight percent, 5 weightpercent to 10 weight percent, 10 weight percent to 90 weight percent, 10weight percent to 70 weight percent, 10 weight percent to 50 weightpercent, 10 weight percent to 25 weight percent, 25 weight percent to 90weight percent, 25 weight percent to 70 weight percent, or 25 weightpercent to 50 weight percent.

The amount of water in the mixed diol stream, based on the total weightof the mixed diol stream, can range from 5 weight percent to 90 weightpercent, 5 weight percent to 70 weight percent, 5 weight percent to 50weight percent, 5 weight percent to 25 weight percent, 5 weight percentto 10 weight percent, 10 weight percent to 90 weight percent, 10 weightpercent to 70 weight percent, 10 weight percent to 50 weight percent, 10weight percent to 25 weight percent, or 25 weight percent to 90 weightpercent, 25 weight percent to 70 weight percent, 25 weight percent to 50weight percent.

The process of the present invention forms a raffinate phase comprisinga major amount of the glycerol and a minor amount of the diols containedin the mixed diol stream. In an aspect of the present invention, greaterthan 90 weight percent of the glycerol is recovered in the raffinatephase. In another aspect, greater than 95 weight percent, greater than98 weight percent, greater than 99 weight percent, or greater than 99.9weight percent of the glycerol is recovered in the raffinate phase.

The process of the present invention forms an extract phase comprising amajor amount of the diols and a minor amount of the glycerol containedin the mixed diol stream. In an aspect of the invention, greater than 60percent of the diols in the mixed diol stream is recovered in theextract phase. In another aspect, greater than 70 weight percent,greater than 80 weight percent, greater than 90 weight percent, greaterthan 98 weight percent, or greater than 99 weight percent of the diolsin the mixed diol stream is recovered in the extract phase.

The extract phase can be back extracted with water to form a second,aqueous extract phase containing a major amount of diols in the second,aqueous extract phase and a minor amount of diols in the second,hydrophobic solvent raffinate phase. The hydrophobic solvent may berecycled to the first extractor to separate glycerol and the diols. Theaqueous, extract phase can become a new mixed diol feed to producepurified ethylene glycol and/or three carbon glycols by the processesdescribed above and below, respectively.

Our process can also be used, for example, to separate glycols from afermentation broth. A fifth embodiment of our invention, is a processfor recovering diols from a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 0.1 weight percent to 30 weight percent of ethylene glycol,        1,2-propanediol and 1,3-propanediol, 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol;    -   (ii) 5 to 50 weight percent glucose; and    -   (iii) 50 weight percent to 90 weight percent water; each based        on the total weight of the mixed diol stream, with an        extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the glucose and a        minor amount of the diols contained in the mixed diol stream and        an extract phase comprising a major amount of the diols and a        minor amount of the glucose contained in the mixed diol stream;        and-   (B) separating the raffinate phase and the extract phase.

The various aspects of hydrophobic solvent, second modifying hydrophobicsolvent, weight percent of hydrophobic solvent and second modifyinghydrophobic solvent in the extractant apply to the present embodiment.

For example, the mixed diol stream can comprise 0.1 weight percent to 30weight percent ethylene glycol, 1 weight percent to 30 weight percentethylene glycol, 1 weight percent to 20 weight percent ethylene glycol,5 weight percent to 30 weight percent ethylene glycol, or 5 weightpercent to 20 weight percent ethylene glycol; 0.1 weight percent to 30weight percent three-carbon diols, 1 weight percent to 30 weight percentthree-carbon diols, 1 weight percent to 20 weight percent three-carbondiols, 5 weight percent to 30 weight percent three-carbon diols, or 5weight percent to 20 weight percent three-carbon diols; and 0.1 weightpercent to 30 weight percent four-carbon diols, 1 weight percent to 30weight percent four-carbon diols, 1 weight percent to 20 weight percentfour-carbon diols, 5 weight percent to 30 weight percent four-carbondiols, 5 weight percent to 20 weight percent four-carbon diols, or 10weight percent to 20 weight percent four-carbon diols, each based on thetotal weight of the mixed diol stream.

The amount of glucose in the mixed diol stream, based on the totalweight of the mixed diol stream, can range from 5 weight percent to 50weight percent, 5 weight percent to 40 weight percent, 5 weight percentto 30 weight percent, 5 weight percent to 20 weight percent, 5 weightpercent to 10 weight percent, 10 weight percent to 50 weight percent, 10weight percent to 40 weight percent, 10 weight percent to 30 weightpercent, 10 weight percent to 20 weight percent, 25 weight percent to 50weight percent, 25 weight percent to 40 weight percent, or 25 weightpercent to 30 weight percent.

The amount of water in the mixed diol stream, based on the total weightof the mixed diol stream, can range from 50 weight percent to 90 weightpercent, 50 weight percent to 80 weight percent, 50 weight percent to 70weight percent, 50 weight percent to 60 weight percent, 60 weightpercent to 90 weight percent, 60 weight percent to 80 weight percent, 60weight percent to 70 weight percent, 70 weight percent to 90 weightpercent, 70 weight percent to 80 weight percent, or 80 weight percent to90 weight percent.

The process of the present invention forms a raffinate phase comprisinga major amount of the glucose and a minor amount of the diols containedin the mixed diol stream. In an aspect of the present invention, greaterthan 90 weight percent of the glucose is recovered in the raffinatephase. In another aspect, greater than 95 weight percent, greater than98 weight percent, greater than 99 weight percent, or greater than 99.5weight percent of the glucose is recovered in the raffinate phase.

The process of the present invention forms an extract phase comprising amajor amount of the diols and a minor amount of the glucose contained inthe mixed diol stream. In an aspect of the invention, greater than 60percent of the diols in the mixed diol stream is recovered in theextract phase. In another aspect, greater than 70 weight percent,greater than 80 weight percent, greater than 90 weight percent, greaterthan 98 weight percent, or greater than 99 weight percent of the diolsin the mixed diol stream is recovered in the extract phase.

The extract phase can be back extracted with water to form a second,aqueous extract phase containing a major amount of diols in the second,aqueous extract phase and a minor amount of diols in the second,hydrophobic solvent raffinate phase. The hydrophobic solvent may berecycled to the first extractor to separate glucose and the diols. Theaqueous, extract phase can become a new mixed diol feed to producepurified ethylene glycol and/or three carbon glycols by the processesdescribed above and below, respectively.

A sixth embodiment of our invention, is a process for recoveringpurified propanediol, from a mixed diol stream comprising propanediolsand butanediols, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 1 weight percent to 99.5 weight percent of one or more        three-carbon diols selected from 1,2-propanediol and        1,3-propanediol;    -   (ii) 20 ppm by weight to 99 weight percent of one or more        four-carbon diols selected from 1,2-butanediol, 1,3-butanediol,        1,4-butanediol, and 2,3-butanediol; each based on the total        weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the three-carbon        diols and a minor amount of the four-carbon diols contained in        the mixed diol stream and an extract phase comprising a major        amount of the four-carbon diols and a minor amount of the        three-carbon diols contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

The various aspects of water content in the mixed diol stream,hydrophobic solvent, second modifying hydrophobic solvent, weightpercent of hydrophobic solvent and second modifying hydrophobic solventin the extractant, extraction process, and extract phase clean-up andlean solvent recycle discussed above apply to the present embodiment.The mixed diol stream may comprise 1 weight percent to 99.5 weightpercent three-carbon diols, 1 weight percent to 95 weight percentthree-carbon diols, 1 weight percent to 90 weight percent three-carbondiols, 1 weight percent to 80 weight percent three-carbon diols, 1weight percent to 70 weight percent three-carbon diols, 10 weightpercent to 99.5 weight percent three-carbon diols, 10 weight percent to95 weight percent three-carbon diols, 10 weight percent to 90 weightpercent three-carbon diols, 10 weight percent to 80 weight percentthree-carbon diols, 10 weight percent to 70 weight percent three-carbondiols, 30 weight percent to 99.5 weight percent three-carbon diols, 30weight percent to 95 weight percent three-carbon diols, 30 weightpercent to 90 weight percent three-carbon diols, 30 weight percent to 80weight percent three-carbon diols, or 30 weight percent to 70 weightpercent three-carbon diols; and 20 ppm to 99.5 weight percentfour-carbon diols, 20 ppm to 95 weight percent four-carbon diols, 20 ppmto 90 weight percent four-carbon diols, 20 ppm to 80 weight percentfour-carbon diols, 20 ppm to 70 weight percent four-carbon diols, 1weight percent to 99.5 weight percent four-carbon diols, 1 weightpercent to 95 weight percent four-carbon diols, 1 weight percent to 90weight percent four-carbon diols, 1 weight percent to 80 weight percentfour-carbon diols, 1 weight percent to 70 weight percent four-carbondiols, 10 weight percent to 99.5 weight percent four-carbon diols, 10weight percent to 95 weight percent four-carbon diols, 10 weight percentto 90 weight percent four-carbon diols, 10 weight percent to 80 weightpercent four-carbon diols, 10 weight percent to 70 weight percentfour-carbon diols, 30 weight percent to 99.5 weight percent four-carbondiols, 30 weight percent to 95 weight percent four-carbon diols, 30weight percent to 90 weight percent four-carbon diols, 30 weight percentto 80 weight percent four-carbon diols, or 30 weight percent to 70weight percent four-carbon diols, each based on the total weight ofdiols.

The process of the present invention forms a raffinate phase comprisinga major amount of the three-carbon diols and a minor amount of thefour-carbon diols contained in the mixed diol stream. In an aspect ofthe present invention, greater than 95 weight percent of thethree-carbon diols in the mixed diol stream is recovered in theraffinate phase. In another aspect, greater than 98 weight percent,greater than 99 weight percent, greater than 99.5 weight percent, orgreater than 99.99 weight percent of the three-carbon diols in the mixeddiol stream is recovered in the raffinate phase.

The process of the present invention forms an extract phase comprising amajor amount of the four-carbon diols and a minor amount of thethree-carbon diols contained in the mixed diol stream. In an aspect ofthe invention, greater than 60 weight percent of the four-carbon diolsin the mixed diol stream is recovered in the extract phase. In anotheraspect, greater than 70 weight percent, greater than 80 weight percent,greater than 90 weight percent, greater than 95 weight percent, greaterthan 98 weight percent, or greater than 99 weight percent of thefour-carbon diols in the mixed diol stream is recovered in the extractphase.

The raffinate phase can be concentrated in three-carbon diols. Theconcentration of the three-carbon diols, based on the total weight ofdiols in the raffinate phase, can be greater than 95 weight percent,greater than 98 weight percent, greater than 99 weight percent, greaterthan 99.9 weight percent, or greater than 99.99 weight percent. Theconcentration of the four-carbon diols, based on the total weight ofdiols in the raffinate phase can be less than 5 weight percent, lessthan 1 weight percent, less than 0.5 weight percent, less than 1000 ppmon a weight basis, less than 500 ppm on a weight basis, or less than 100ppm on a weight basis.

The forward extraction of the mixed diol stream also produces araffinate phase which, in addition to three-carbon diols, can comprisefour-carbon diols, water, and hydrophobic solvent. The raffinate phasecan be further processed to recover a high-purity three-carbon diolproduct. For example, the raffinate phase can be fed to a distillationcolumn where water and hydrophobic solvent can be separated from thethree-carbon diols. The hydrophobic solvent can be further processedand/or recycled to the extractor.

FIGS. 1 and 2 present two, non-limiting embodiments of the instantinvention, described herein in detail. In a first embodiment of theinvention as laid out in FIG. 1, Mixed Diol Feed Stream 6 is fedcounter-currently to Forward Extractor 1, wherein the stream isimmediately contacted with Extractant Stream 21. Two products exitForward Extractor 1, the Hydrophilic Raffinate Product Stream 8,depleted of higher-number-carbon diols, and Hydrophobic Extract ProductStream 7. An additional hydrophobic solvent Stream 14, preferably onethat forms an azeotrope with the higher-carbon-number diols, can bemixed with Stream 7 before Stream 7 is fed to a distillation column,Solvent Column 2. A Lean Hydrophobic Solvent Stream 19, reduced in theamount of diols, exits as the bottoms product of Solvent Column 2. LeanHydrophobic Solvent Stream 19 is recycled back to Forward Extractor 1:Stream 19 is combined with Solvent Make-up Stream 20 to produceExtractant Stream 21 which is fed to Forward Extractor 1. An azeotropiccomposition comprising diols, hydrophobic solvent, and/or water exitsthe top of Solvent Column 2 as Stream 15. Stream 15 is condensed andphases are allowed to separate in Decanter 3. Part of the hydrophobicphase is refluxed back to Solvent Column 2 as Stream 18 and part can bepurged or sent for further processing as Stream 16. The hydrophilicphase, containing the majority of the diols, can be sent for furtherprocessing as Stream 17.

Raffinate Hydrophilic Product Stream 8 from Forward Extractor 1 is richin ethylene glycol. Stream 8 can be sent to a distillation column,Refining Column 4, to produce a purified ethylene glycol bottoms Stream13. Stream 9, exiting the top of Refining Column 4 can comprise water,hydrophobic solvent, higher-carbon-number diols, and/or ethylene glycol.Stream 9 is condensed and allowed to phase separate in Decanter 5. Partof the hydrophobic phase is refluxed back to Refining Column 4 as Stream12 and part can be purged or sent for further processing as Stream 10.The hydrophilic phase can be sent for further processing as Stream 11.

In the previously described first embodiment of the instant invention,conventional extraction, i.e., extraction involving a single solventfeed point is utilized for the forward extraction zone. It may beadvantageous, however, to operate the forward extraction zone as afractional counter-current extraction in which additional hydrophobicsolvent components or hydrophilic solvent components are introduced asseparate feeds. In a second embodiment of the invention as set forth inFIG. 2, Hydrophilic Solvent Stream 6 is optionally split into Stream 7and Stream 8 wherein Stream 8 is combined with Mixed Diol Feed Stream 5to produce Stream 21. Stream 21 is fed counter-currently to ForwardExtractor 1, wherein the stream is intimately contacted with HydrophobicSolvent Stream 20. When operated as a fractional extractor, Stream 7 isintroduced into Forward Extractor 1 above feed Stream 21. Two productsexit Forward Extractor 1, the Hydrophilic Raffinate Diol Product Stream10 rich in ethylene glycol and the Hydrophobic Solvent Extract Stream 9rich in higher-carbon-number diols. The purpose of feed Stream 7 is tofurther reduce losses of lower-carbon-number diols (e.g., ethyleneglycol) into Stream 9. Stream 9 is fed counter-currently to a secondextraction zone, Back Extractor 2, wherein the stream is intimatelycontacted with Water Stream 11. Two products are withdrawn from BackExtractor 2, the Hydrophobic Raffinate Stream 12 comprising the leanhydrophobic solvent which is recycled to Forward Extractor 1, and theHydrophilic Extract Stream 13 comprising higher-carbon-number diols.Stream 13 is refined via distillation in Solvent Column 3. Bottomsproduct, Stream 18, comprises water and diols. Stream 14 exiting the topof Solvent Column 3 is condensed and the phases are allowed to separatein Decanter 4. Part of the hydrophobic phase is refluxed to SolventColumn 3 in Stream 17 and part of the hydrophobic phase is purged orsent for further processing in Stream 15. A hydrophilic phase is purgedor sent for further processing in Stream 16.

The efficiency of the extraction process of the invention can bemeasured by a partition coefficient, abbreviated herein as “P(A)” of adiol component “A” which is defined as the concentration of diolcomponent “A” in the hydrophobic phase divided by the concentration ofdiol component “A” in the hydrophilic phase. The partition coefficientmay be determined by analysis of diol component “A” by known methodssuch as, for example, gas chromatography.

When the one or more higher-carbon-number diols (“H”) are partitionedbetween the hydrophilic phase and the hydrophobic phase by theextraction processes of the invention, the P(H) value of diol component“H” can be maintained at a level greater than about 0.4, greater thanabout 0.5, or greater than about 0.7, depending on the efficiency of theextraction process. If the P(H) value is high, diol component “H” willpreferentially distribute into the hydrophobic phase. Similarly, theefficiency of the extraction process can be measured by a partitioncoefficient of one or more lower-carbon-number diols (“L”). Thepartition coefficient P(L) value of diol component “L” can be less thanabout 0.5, less than about 0.4, or less than about 0.25, depending onthe efficiency of the extraction process. For example, if a mixture ofethylene glycol, 1,2-propanediol, 1,2-butane diol, and water arevigorously mixed with a hydrophobic solvent and allowed to phaseseparate, the 1,2-butanediol can desirably have a partition coefficientP(1,2-BDO) greater than about 0.4, greater than about 0.5, or greaterthan 0.7 and ethylene glycol can desirably have a partition coefficientP(EG) less than 0.5, less than 0.4, or less than 0.25.

In an aspect, the extraction process of this invention can be conductedin a manner such that a separation criterion is satisfied. The criterionreferred to herein as selectivity between diol components “H” and “L”,is based on ratio of the partition coefficients defined above. Forexample, the selectivity (“S”) between “H” and “L” is a partitioncoefficient ratio, S=P(H)/P(L). The S value for this ratio can bemaintained at a level greater than about 1.5. Other values of S includegreater than about 2.2 and greater than about 3.0. If the S value ishigh, the extraction will effectively and efficiently separate the keyhigher-carbon-number diol components and lower-carbon-number diolcomponents, “H” and “L”, into the extract and raffinate phasesrespectively.

The invention also includes the following non-limiting embodiments thatare set forth below.

A First Embodiment is a process for recovering purified ethylene glycolfrom a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 1 weight percent to 99.5 weight percent, ethylene glycol;    -   (ii) 20 ppm by weight to 99 weight percent of one or more        three-carbon diols and four-carbon diols selected from        1,2-propanediol, 1,3-propanediol, 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol; each based        on the total weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms;        -   to form a raffinate phase comprising a major amount of the            ethylene glycol and a minor amount of the three-carbon diols            and/or four-carbon diols contained in the mixed diol stream            and an extract phase comprising a major amount of the            three-carbon diols and/or four-carbon diols and a minor            amount of the ethylene glycol contained in the mixed diol            stream; and-   (B) separating the raffinate phase and the extract phase.

The process of the First Embodiment wherein the mixed diol streamcomprises 20 weight percent to 99.5 weight percent ethylene glycol, 20ppm by weight to 40 weight percent of three-carbon diols, and 20 ppm byweight to 30 weight percent four-carbon diols.

The process of the First Embodiment wherein the mixed diol streamcomprises 10 weight percent to 60 weight percent ethylene glycol, 40weight percent to 90 weight percent three-carbon diols, and 0.1 weightpercent to 10 weight percent four-carbon diols.

The process of the First Embodiment wherein the mixed diol streamcomprises 20 weight percent to 45 weight percent ethylene glycol, 50weight percent to 65 weight percent three-carbon diols, and 3 weightpercent to 9 weight percent four-carbon diols.

The process of the First Embodiment wherein the mixed diol streamcomprises 20 weight percent to 60 weight percent ethylene glycol, 30weight percent to 70 weight percent three-carbon diols, and 5 weightpercent to 25 weight percent four-carbon diols.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said mixed diol streamcomprises from 0.5 weight percent to 25 weight percent water, 5 weightpercent to 50 weight percent water, 5 weight percent to 35 weightpercent water, 10 weight percent to 40 weight percent water, or 15weight percent to 35 weight percent water.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said hydrophobic solvent isselected from 2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutylketone, methyl isopropyl ketone, methyl propyl ketone, diisobutylketone, trioctylphosphine oxide, trihexylphosphine oxide, and mixturesthereof.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said hydrophobic solvent isselected from 2-ethylhexanol, cyclohexanol, trioctylphosphine oxide,trihexylphosphine oxide, and mixtures thereof.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said hydrophobic solvent isselected from 2-ethylhexanol, trioctylphosphine oxide, trihexylphosphineoxide, and mixtures thereof.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said second modifyinghydrophobic solvent is selected from hexane, heptane, octane, decane,benzene, toluene, xylenes, isoparaffinic mixed hydrocarbons having aboiling range between 90 and 325° C., methyl napththalenes, and mixturesthereof.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said second modifyinghydrophobic solvent is selected from heptane, decane, isoparaffinicmixed hydrocarbons having a boiling range between 90 and 325° C., andmixtures thereof.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said extractant comprises50 weight percent to 100 weight percent of said hydrophobic solvent and0 weight percent to 50 weight percent of said second modifyinghydrophobic solvent, or 60 weight percent to 95 weight percent of saidhydrophobic solvent and 5 weight percent to 40 weight percent of saidsecond modifying hydrophobic solvent, or 70 weight percent to 90 weightpercent of said hydrophobic solvent and 10 weight percent to 30 weightpercent of said second modifying hydrophobic solvent.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein greater than 95 weightpercent, or greater than 98 weight percent, or greater than 99 weightpercent, or greater than 99.5 weight percent, or greater than 99.9weight percent of said ethylene glycol in said mixed diol stream isrecovered in said raffinate phase.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein greater than 80 weightpercent, or greater than 85 weight percent, or greater than 90 weightpercent, or greater than 95 weight percent, or greater than 98 weightpercent, or greater than 99 weight percent, or greater than 99.9 weightpercent of said four-carbon diols are recovered in said extract phase.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein the purity of said ethyleneglycol in said raffinate phase is greater than 95 weight percent, orgreater than 98 weight percent, or greater than 99 weight percent, orgreater than 99.9 weight percent, or greater than 99.99 weight percent,based the total weight of said diols.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein the total amount of saidthree-carbon diols and said four-carbon diols in said raffinate phase isless than 5 weight percent, less than 1 weight percent, less than 0.5weight percent, less than 1000 ppm by weight, less than 500 ppm byweight, or less than 100 ppm by weight, based on the total weight ofsaid diols.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said extraction occurs in acontinuous counter-current extractor, wherein said extractant is fedlower to said extractor than said mixed diol stream, and wherein thefeed ratio of said extractant to said mixed diol stream ranges from0.5:1 to 20:1, or 1:1 to 10:1, or 1:1 to 5:1.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said extraction occurs in acontinuous counter-current extractor, wherein said extractant is fedlower to said extractor than said mixed diol stream, and wherein thefeed ratio of said extractant to said mixed diol stream ranges from0.5:1 to 20:1, or 1:1 to 10:1, or 1:1 to 5:1, further comprising feedinga hydrophilic stream to said extractor at a higher level than said mixeddiol stream and wherein the feed ratio of said hydrophilic stream tosaid mixed diol stream ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or0.1:1 to 0.8:1.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said extraction occurs in acontinuous counter-current extractor, wherein said extractant is fedlower to said extractor than said mixed diol stream, and wherein thefeed ratio of said extractant to said mixed diol stream ranges from0.5:1 to 20:1, or 1:1 to 10:1, or 1:1 to 5:1, further comprising feedinga hydrophilic stream to said extractor at a higher level than said mixeddiol stream and wherein the feed ratio of said hydrophilic stream tosaid mixed diol stream ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or0.1:1 to 0.8:1, and wherein the hydrophilic stream comprises water.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, wherein said extraction occurs in acontinuous counter-current extractor, wherein said extractant is fedlower to said extractor than said mixed diol stream, and wherein thefeed ratio of said extractant to said mixed diol stream ranges from0.5:1 to 20:1, or 1:1 to 10:1, or 1:1 to 5:1, wherein said hydrophilicsolvent comprises water, and wherein said extraction occurs in saidextractor over 4 to 20 theoretical stages, or over 6 to 18 theoreticalstages, or over 10 to 15 theoretical stages.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, further comprising removing amajority of said three-carbon diols and said four-carbon diols from saidextract phase to form a lean solvent and recycling said lean solvent,whereby said extractant comprises at least a portion of said leansolvent.

The process of the First Embodiment or the First Embodiment with any oneor more of the intervening features, further comprising removing amajority of said three-carbon diols and said four-carbon diols from saidextract phase to form a lean solvent and recycling said lean solventwhereby said extractant comprises at least a portion of said leansolvent, wherein the removing occurs through back extraction or throughdistillation.

A Second Embodiment is a process for recovering purified ethylene glycolfrom a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 20 weight percent to 99.5 weight percent, ethylene glycol;    -   (ii) 20 ppm by weight to 40 weight percent of one or more        three-carbon diols selected from 1,2-propanediol and        1,3-propanediol, and 20 ppm by weight to 30 weight percent of        one or more four-carbon diols selected from 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol; each based        on the total weight of diols, and    -   (iii) 5 weight percent to 35 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from 2-ethylhexanol,        cyclohexanol, n-hexanol, methyl isobutyl ketone, methyl        isopropyl ketone, methyl propyl ketone, diisobutyl ketone,        trioctylphosphine oxide, trihexylphosphine oxide, and mixtures        thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hexane, heptane, octane, decane, benzene, toluene, xylenes,        isoparaffinic mixed hydrocarbons having a boiling range between        90 and 325° C., methyl napththalenes, and mixtures thereof;        -   to form a raffinate phase comprising a major amount of the            ethylene glycol and a minor amount of the three-carbon diols            and/or four-carbon diols contained in the mixed diol stream            and an extract phase comprising a major amount of the            three-carbon diols and/or four-carbon diols and a minor            amount of the ethylene glycol contained in the mixed diol            stream; and-   (B) separating the raffinate phase and the extract phase.

The process of the Second Embodiment wherein greater than 95 weightpercent, or greater than 99 weight percent, or greater than 99.5 weightpercent of said ethylene glycol in said mixed diol stream is recoveredin said raffinate phase, and wherein greater than 60 weight percent, orgreater than 80 weight percent, or greater than 90 weight percent ofsaid four-carbon diols is recovered in said extract phase, and whereinthe concentration of said ethylene glycol in said raffinate phase isgreater than 95 weight percent, or greater than 99 weight percent, orgreater than 99.5 weight percent and the concentration of saidthree-carbon diols and said four-carbon diols combined in said raffinateis less than 1 weight percent, or less than 1000 ppm, or less than 500ppm, each based on the total weight of said diols.

The process of the Second Embodiment or the Second Embodiment with anyone or more of the intervening features wherein said extraction occursin a continuous counter-current extractor, wherein said extractant isfed lower to said extractor than said mixed diol stream, wherein thefeed ratio of said extractant to said mixed diol stream ranges from0.5:1 to 20:1, or 1:1 to 10:1, or 1:1 to 5:1; further comprising feedinga hydrophilic stream to said extractor at a higher level than said mixeddiol stream, wherein the feed ratio of said hydrophilic stream to saidmixed diol stream ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or 0.1:1to 0.8:1; and wherein said hydrophilic stream comprises water.

A Third embodiment is a process for recovering purified ethylene glycolfrom a mixed diol stream comprising ethylene glycol and four-carbondiols, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 50 weight percent to 99.99 weight percent ethylene glycol;    -   (ii) 0.01 weight percent to 50 weight percent of one or more        four-carbon diols selected from 1,2-butanediol, 1,3-butanediol,        1,4-butanediol, and 2,3-butanediol; each based on the total        weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the ethylene glycol        and a minor amount of the four-carbon diols contained in the        mixed diol stream and an extract phase comprising a major amount        of the four-carbon diols and a minor amount of the ethylene        glycol contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

The process of the Third Embodiment wherein said hydrophobic solvent isselected from 2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutylketone, methyl isopropyl ketone, methyl propyl ketone, diisobutylketone, trioctylphosphine oxide, trihexylphosphine oxide, and mixturesthereof.

The process of the Third Embodiment or the Third Embodiment with any oneor more of the intervening features wherein greater than 95 weightpercent, greater than 99 weight percent, or greater than 99.5 weightpercent of said ethylene glycol in said mixed diol stream is recoveredin said raffinate phase, and wherein greater than 60 weight percent, orgreater than 80 weight percent, or greater than 90 weight percent ofsaid four-carbon diols is recovered in said extract phase, and whereinthe concentration of said ethylene glycol in said raffinate phase isgreater than 95 weight percent, or greater than 99 weight percent, orgreater than 99.5 weight percent and the concentration of saidfour-carbon diols in said raffinate is less than 1 weight percent, orless than 1000 ppm, or less than 500 ppm, each based on the total weightof said diols.

The process of the Third Embodiment or the Third Embodiment with any oneor more of the intervening features wherein said extraction occurs in acontinuous counter-current extractor, wherein said extractant is fedlower to said extractor than said mixed diol stream, wherein the feedratio of said extractant to said mixed diol stream ranges from 0.5:1 to20:1, or 1:1 to 10:1, or 1:1 to 5:1; further comprising feeding ahydrophilic stream to said extractor at a higher level than said mixeddiol stream, wherein the feed ratio of said hydrophilic stream to saidmixed diol stream ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or 0.1:1to 0.8:1; and wherein said hydrophilic stream comprises water.

A Fourth Embodiment of our invention, is a process for recovering diolsfrom a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 0.1 weight percent to 50 weight percent of one or more diols        selected from ethylene glycol, 1,2-propanediol, 1,3-propanediol        1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and        2,3-butanediol;    -   (ii) 5 weight percent to 90 weight percent glycerol; and    -   (iii) 5 weight percent to 90 weight percent water; each based on        the total weight of the mixed diol stream with an extractant,        comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the glycerol and a        minor amount of the diols contained in the mixed diol stream and        an extract phase comprising a major amount of the diols and a        minor amount of the glycerol contained in the mixed diol stream;        and-   (B) separating the raffinate phase and the extract phase.

The process of the Fourth Embodiment wherein said hydrophobic solvent isselected from 2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutylketone, methyl isopropyl ketone, methyl propyl ketone, diisobutylketone, trioctylphosphine oxide, trihexylphosphine oxide, and mixturesthereof.

The process of the Fourth Embodiment or the Fourth Embodiment with anyone or more intervening features wherein greater than 90 weight percent,greater than 95 weight percent, greater than 98 weight percent, greaterthan 99 weight percent, or greater than 99.5 weight percent of saidglycerol is recovered in said raffinate phase and wherein greater than60 weight percent, greater than 70 weight percent, greater than 80weight percent, greater than 90 weight percent, greater than 98 weightpercent, or greater than 99 weight percent of said diols is recovered insaid extract phase.

The process of the Fourth Embodiment or the Fourth Embodiment with anyone or more of the intervening features wherein said extraction occursin a continuous counter-current extractor, wherein said extractant isfed lower to said extractor than said mixed diol stream, wherein thefeed ratio of said extractant to said mixed diol stream ranges from0.5:1 to 20:1, or 1:1 to 10:1, or 1:1 to 5:1; further comprising feedinga hydrophilic stream to said extractor at a higher level than said mixeddiol stream, wherein the feed ratio of said hydrophilic stream to saidmixed diol stream ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or 0.1:1to 0.8:1, and wherein said hydrophilic stream comprises water.

A Fifth Embodiment of our invention, is a process for recovering diolsfrom a mixed diol stream, comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 0.1 weight percent to 30 weight percent of ethylene glycol,        1,2-propanediol and 1,3-propanediol, 1,2-butanediol,        1,3-butanediol, 1,4-butanediol, and 2,3-butanediol;    -   (ii) 5 to 50 weight percent glucose; and    -   (iii) 50 weight percent to 90 weight percent water; each based        on the total weight of the mixed diol stream, with an        extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the glucose and a        minor amount of the diols contained in the mixed diol stream and        an extract phase comprising a major amount of the diols and a        minor amount of the glucose contained in the mixed diol stream;        and-   (B) separating the raffinate phase and the extract phase.

The process of the Fifth Embodiment wherein said hydrophobic solvent isselected from 2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutylketone, methyl isopropyl ketone, methyl propyl ketone, diisobutylketone, trioctylphosphine oxide, trihexylphosphine oxide, and mixturesthereof.

The process of the Fifth Embodiment or the Fifth Embodiment with any oneor more of the intervening features wherein greater than 90 weightpercent, greater than 95 weight percent, greater than 98 weight percent,greater than 99 weight percent, or greater than 99.5 weight percent ofsaid glucose is recovered in said raffinate phase and wherein greaterthan 60 weight percent, greater than 70 weight percent, greater than 80weight percent, greater than 90 weight percent, greater than 98 weightpercent, or greater than 99 weight percent of diols is recovered in saidextract phase.

The process of the Fifth Embodiment or the Fifth Embodiment with any oneor more of the intervening features wherein said extraction occurs in acontinuous counter-current extractor, wherein said extractant is fedlower to said extractor than said mixed diol stream, wherein the feedratio of said extractant to said mixed diol stream ranges from 0.5:1 to20:1, or 1:1 to 10:1, or 1:1 to 5:1; further comprising feeding ahydrophilic stream to said extractor at a higher level than said mixeddiol stream, wherein the feed ratio of said hydrophilic stream to saidmixed diol stream ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or 0.1:1to 0.8:1, and wherein said hydrophilic stream comprises water.

A Sixth Embodiment is a process for recovering purified three-carbondiols from a mixed diol stream comprising propanediols and butanediols,comprising

-   (A) extracting the mixed diol stream, comprising    -   (i) 1 weight percent to 99.5 weight percent of one or more        three-carbon diols selected from 1,2-propanediol and        1,3-propanediol;    -   (ii) 20 ppm by weight to 99 weight percent of one or more        four-carbon diols selected from 1,2-butanediol, 1,3-butanediol,        1,4-butanediol, and 2,3-butanediol; each based on the total        weight of diols, and    -   (iii) 0 weight percent to 50 weight percent water, based on the        total weight of diols and water, with an extractant, comprising    -   (i) a hydrophobic solvent selected from alkanols having from 6        to 20 carbon atoms, ketones having from 5 to 20 carbon atoms,        esters having from 5 to 20 carbon atoms, ethers having from 5 to        20 carbon atoms, carboxylic acids having from 5 to 20 carbon        atoms, trialkylphosphine oxides having from 18 to 48 carbon        atoms, and mixtures thereof; and    -   (ii) optionally, a second modifying hydrophobic solvent selected        from hydrocarbons having from 5 to 20 carbon atoms; to form a        raffinate phase comprising a major amount of the three-carbon        diols and a minor amount of the four-carbon diols contained in        the mixed diol stream and an extract phase comprising a major        amount of four four-carbon diols and a minor amount of the        three-carbon diols contained in the mixed diol stream; and-   (B) separating the raffinate phase and the extract phase.

The process of the Sixth Embodiment wherein said hydrophobic solvent isselected from 2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutylketone, methyl isopropyl ketone, methyl propyl ketone, diisobutylketone, trioctylphosphine oxide, trihexylphosphine oxide, and mixturesthereof.

The process of the Sixth Embodiment or the Sixth Embodiment with any oneor more of the intervening features wherein greater than 95 weightpercent, greater than 99 weight percent, or greater than 99.5 weightpercent of said three-carbon diols in said mixed diol stream isrecovered in said raffinate phase, and wherein greater than 60 weightpercent, or greater than 80 weight percent, or greater than 90 weightpercent of said four-carbon diols is recovered in said extract phase,and wherein the concentration of said three-carbon diols in saidraffinate phase is greater than 95 weight percent, or greater than 99weight percent, or greater than 99.5 weight percent and theconcentration of said four-carbon diols in said raffinate is less than 1weight percent, or less than 1000 ppm, or less than 500 ppm, each basedon the total weight of said diols.

The process of the Sixth Embodiment or the Sixth Embodiment with any oneor more of the intervening features wherein said extraction occurs in acontinuous counter-current extractor, wherein said extractant is fedlower to said extractor than said mixed diol stream, wherein the feedratio of said extractant to said mixed diol stream ranges from 0.5:1 to20:1, or 1:1 to 10:1, or 1:1 to 5:1; further comprising feeding ahydrophilic stream to said extractor at a higher level than said mixeddiol stream, wherein the feed ratio of said hydrophilic stream to saidmixed diol stream ranges from 0.05:1 to 2:1, or 0.1:1 to 1.5:1, or 0.1:1to 0.8:1; and wherein said hydrophilic stream comprises water.

The invention is further illustrated by the following, non-limitingexamples.

EXAMPLES General

Analyses of mixed diol products and various extraction phases werecarried out by gas chromatography (“GC”) using the following procedure.The components from the glycolic acid hydrogenation reaction were firstreacted with BSTFA [N,O-bis(trimethylsilyl)trifluoroacetamide] in thepresence of pyridine to the corresponding TMS-derivatives includingwater, which were then separated and quantified by an internal standard(decane) wt % calibrated GC method. The sample to derivatization reagent(BSTFA and pyridine) ratio was 0.1 g:1 ml:0.2 ml in a GC vial, which washeated at 80° C. for 30 minutes to ensure complete derivatization. TheGC method used a DB-1301 capillary column or equivalent (6%cyanopropylphenyl/94% dimethylpolysiloxane stationary phase, 60meters×0.32 mm ID×1.0 um film thickness), a split injector (280° C.), aflame ionization detector (300° C.), helium carrier gas at a constantlinear velocity of 27 cm/sec (a Shimadzu GC 2010 or equivalent) or at aninitial column head pressure of 17 psi, an oven temperature program of80° C. initial temp for 6 min, 4° C./min temp ramp rate to 150° C. for 0min and 10° C./min temp ramp rate to 290° C. for 17.5 min final holdtime. 1-ul of the prepared sample solution was injected with a splitratio of 40:1. The method provided quantification range of 0.01-100 wt %for each analyte within its separation capability.

For all extraction examples the partition coefficient for component A isdefined as follows:

${P(A)} = \frac{{Weight}\mspace{14mu}{Percent}\mspace{14mu} A\mspace{14mu}{in}\mspace{14mu}{Hydrophobic}\mspace{14mu}{phase}}{{Weight}\mspace{14mu}{Percent}\mspace{14mu} A\mspace{14mu}{in}\mspace{14mu}{Hydrophilic}\mspace{14mu}{phase}}$Selectivity between components A and B is defined as:S(AB)=P(A)/P(B)Throughout the examples, the following abbreviations are used in theTables:

Compound Abbreviation(2-(butoxymethyl)-2-((diphenylphosphino)methyl)propane- BuO-triphos1,3-diyl)-bis(diphenylphosphine) Ethylene glycol EG 1,3-Butanediol1,3-BDO 1,2-Butanediol 1,2-BDO 1,4-Butanediol 1,4-BDO 2,3-Butanediol2,3-BDO 1,2-Propanediol 1,2-PDO 1,3-Propanediol 1,3-PDO Cyanex 923 C9232-Ethylhexanol 2-EH Isobutyl isobutyrate IBIB Methyl isobutyl ketoneMIBK Diisopropyl ether DIPE Ethyl acetate EA n-butyl acetate NBAIsobutyl acetate IBA Isopropyl acetate IPA n-propyl acetate NPAEthylhexyl acetate EHA Ethyl propionate EP Methyl valerate MVn-propylpropionate NPP Methyl propionate MP Methyl butyrate MB5-ethyl-2-nonanone 5E2N 2-heptanone MAK Diisobutyl ketone DIBK3-methyl-2-butanone MIPK 6-methyl-2-hexanone MIAK TXIB TXIB Tert-butylmethyl ether MTBE Dibutyl ether DBE Diethyleneglycol dibutyl etherDEGDBE Toluene TOL 2-pentanone MPK Propylene carbonate PC N-Hexanol NHCyclohexanol CH Isophorone IPH n-Decanol ND n-Heptane HEP

Glycolic Acid/Ester Feed and Extractant Mixture

A mixture glycolic acid and glycolate esters was prepared by heating amixture of 4000 g of glycolic acid and 1795 grams of ethylene glycol ata temperature of about 100 to about 150° C. under atmospheric pressurewhile removing the water with a Dean-Stark trap. After approximately 860g of water were removed, the reaction pressure was lowered to 25 torrand the reaction was continued until a total 947 g of water werecollected. Mixtures of glycolic acid and glycolate esters preparedaccording to this procedure typically contained about 2 wt % ethyleneglycol, 4 wt % glycolic acid, 2 wt % glycolic acid dimer, 32 wt %glycolic acid monoesters of ethylene glycol (23 wt % glycolic acidmonomer ester of EG, 8 wt % glycolic acid dimer monoester of EG, 2 wt %glycolic acid trimer monoester of EG), and 60 wt % bis-glycolate estersof EG (19 wt % glycolic acid monomer diester of EG, 11 wt % glycolicacid dimer/glycolic acid monomer diester of EG, 4 wt % glycolic acidtrimer/glycolic acid monomer diester of EG, 30 wt % higher glycolic acidoligomer diesters of EG). The above weight percentages are shown for thecomponents that were detected by GC and do not represent all of thecomponents present in the glycolic acid/ester mixture because of thepresence of higher molecular weight oligomers of glycolic acid that donot elute leanly by gas chromatography. These mixtures were used as thefeed for glycolic acid hydrogenation reaction as described in Example 2below.

Example 1 Synthesis of Pentaerythrityl Trichlorohydrin (IX)

A five liter three neck round-bottom flask equipped with an overheardstirrer, a condenser (with a nitrogen purge and a Vigreux column toscrub off any sulfur dioxide), a “Y” connector, with a thermocouple inone side and an addition funnel in the other, was charged with 417 g(3.00 mol) of pentaerythritol and 730 g (9.24 mol) of pyridine. Withvigorous stirring, 1134 g (9.24 mol) of thionyl chloride was chargeddrop wise over a period of 3 hours and 45 minutes and the mixture washeated to 125° C. and held at 125° C. overnight. The brown-yellowsolution was cooled to room temperature and 2 L of cold, deionized waterwas charged with stirring. The precipitate was filtered and washed with2.5 L of cold, deionized water. The vacuum-dried crude product, (459.7g), a 1:3.1 mixture of pentaerythrityl trichlorohydrin (VIII) andpentaerythrityltetrachloride (IX) as determined by NMR, was separatedusing fractional distillation under reduced pressure and recrystallizedfrom cyclohexane to yield 253.5 g of (8). ¹H NMR of 8 (CDCl³): δ 3.74(s, 3H); 3.66 (s, 6H); 1.72 (br, 1H). ¹³C{1H} NMR of 8 (CDCl³): δ 61.2,46.7, 44.0 ppm.

Synthesis of 1-(3-Chloro-2,2-bis(chloromethyl)propoxy)butane (X)

A 300 mL four neck round-bottom flask equipped with an overheardstirrer, a condenser (with a nitrogen purge) and a thermocouple wascharged with 10 g (0.050 mol) of (VIII), 21.68 g (0.16 mol) of1-bromobutane and 52.50 mL of anhydrous DMSO. The flask was cooled in anice/water bath and 12.72 g (0.21 mol) of finely ground KOH was chargedwith vigorous stirring. When no further exotherm was observed, thereaction mixture was heated to 60° C. for 3 hours with stirring. Aftercooling to room temperature, 225 mL of deionized water was chargedslowly. The aqueous phase was extracted with dichloromethane (50 mL)four times. The combined organic layers were washed with 250 mL of 2MHCl, 2×150 mL of deionized water and then dried over Na₂SO₄. Afterfiltration, the solvent was removed using a rotary evaporator. Product(X) was obtained as a faint yellow liquid. Yield: 11.20 g (0.042 mol,80%). ¹H NMR (CDCl₃): δ 3.65 (s, 6H); 3.46 (s, 2H); 3.44 (t, 2H); 1.56(m, 2H); 1.36 (m, 2H); 0.92 (m, 3H). ¹³C{1H} NMR (CDCl₃): δ 71.4, 68.0,46.2, 44.5, 31.6, 19.3, 13.8 ppm.

Synthesis of(2-(butoxymethyl)-2-((diphenylphosphino)methyl)propane-1,3-diyl)bis(diphenylphosphine)(IV)

A 500 mL three neck round-bottom flask containing 283 g (0.30 mol) of adiethoxymethane (DEM) solution of lithium diphenylphosphide was cooledto −78° C. using a dry ice/acetone bath. To this solution, 23.75 g (0.10mol) of compound (X) was charged over a period of 30 minutes with anArgon purge. After all of compound (X) was charged, the acetone/dry icebath was removed, the mixture was allowed to warm to room temperature,and stirred overnight. All volatiles were removed under vacuum, and theresidue was extracted with 50 mL of toluene two times. The extract waswashed with 50 mL of deionized water three times. The organic phase wasdried over Na₂SO₄, filtered, and the volatiles were removed undervacuum. 49.5 g (about 74% crude yield and 92% purity) of sticky solidwas obtained after drying overnight under vaccum. ³¹P{1H} NMR (CDCl₃): δ−26.3 ppm (s). ¹H NMR (CDCl₃): δ 7.50-7.34 (m, 30H); 3.29 (s, 2H); 2.85(t, 2H); 2.71 (s, 6H); 1.24 m (5H); 0.90 (t, 3H). ¹³C{1H} NMR (CDCl₃): δ139.9 (d), 132.9 (d), 128.0 (s), 76.1 (q), 70.3 (s), 42.5 (q), 38.2 (m),31.4 (s), 19.2 (s), 14.0 (s) ppm.

Example 2 Hydrogenation of Glycolic Acid and Glycolate Esters

A mixture comprising 70 ml ethylene glycol, and 6 mL of the glycolicacid/ester feed mixture described above, containing 5 weight percentwater, and(2-(butoxymethyl)-2-((diphenylphosphino)methyl)propane-1,3-diyl)bis(diphenylphosphine)ruthenium diacetate (referred to herein as “(BuO-triphos)Ru(OAc)₂”) at aconcentration of 100 ppm Ru metal was loaded into a high pressureHastelloy C autoclave. The autoclave, nominally 100 mL volume, wasfitted with a Rushton turbine impeller, baffles, thermowell, and gasinlet tube. The reactor vessel was heated electrically to 190° C. by aband heater, with temperature control provided by feedback via a K-typethermocouple in the autoclave thermowell. Pure hydrogen gas (>99.9volume %) was fed to the autoclave via a Brooks flow controller, withpressure maintained at 124.1 bars gauge (1800 psig). After the initialcharge, a stock solution of the glycolic acid/ester feed mixturedescribed above containing 5 weight percent water and(butoxy-triphos)Ru(OAc)₂, at a concentration of 100 ppm Ru metal was fedfor five hours at a rate of 0.4 mL/min. After five hours, the feed ratewas cut to 0.197 mL/min (feed substrate rate of 0.192 ml/min, and thecatalyst rate of 0.005 mL/min). Aliquots of reactor material were takenoff every five minutes to maintain the liquid level at approximately71-72.5 mL. The cumulative reactor effluent was found by GC analysis tocomprise 85.23 weight percent ethylene glycol, 3.39 weight percentglycolate mono esters of ethylene glycol, 4.5 weight percent water, 0.3weight percent glycolic acid, and 0.5 weight percent glycolate diestersof ethylene glycol. X-ray analysis showed the reactor effluent tocomprise 27.9 ppm Ru metal and 23.5 ppm phosphorus content.

Example 3

This example illustrates the effect of water content in the glycolicacid hydrogenation effluent feed mix and the effect of hydrocarboncontent of the extractant on extraction of ethylene glycol,1,2-butanediol (BDO), and 1,2-propanediol (PDO). In Experiments 3-1 to3-20, water was added to the reactor effluent generated in Example 2 togive the water content specified in Table 1. In addition, 1 weightpercent (on an undiluted reactor effluent basis) each of BDO and PDO wasadded to the reaction effluent of Example 2. The resulting mixtures werecontacted (i.e., mixed vigorously) with a solvent mixture comprising2-ethylhexanol and heptane in the composition and solvent to feed (S/F)ratio specified in Table 1. Each mixture was held at 60° C., allowed toseparate into two clear phases and analyzed by GC to determine EG,1,2-PDO, 1,2-BDO weight percentages which were used to calculatepartition coefficients (P) of ethylene glycol, 1,2-BDO, and 1,2-PDO andselectivities between EG and the two other diols. The ethylene glycol,1,2-propanediol, and 1,2-butanediol partition coefficients (abbreviatedas P(EG), P(1,2-PDO), and P(1,2-BDO)) and selectivities (abbreviated asS(1,2-PDO/EG), and S(1,2-BDO/EG)) are summarized in Table 1.

TABLE 1 Wt % Wt % S/F Water in Heptane in Ex. Ratio Feed Mix Solvent MixP(EG) P(1,2-PDO) P(1,2-BDO) S(1,2-PDO/EG) S(1,2-BDO/EG) 3-1 0.99 9.89%0.0% 0.46 0.63 0.87 1.37 1.89 3-2 1.00 14.00% 0.0% 0.31 0.50 0.79 1.612.55 3-3 0.99 23.71% 0.0% 0.21 0.37 0.68 1.76 3.24 3-4 1.00 33.25% 0.0%0.16 0.31 0.63 1.94 3.94 3-5 1.00 9.89% 10.0% 0.32 0.48 0.72 1.50 2.253-6 0.99 14.00% 10.0% 0.23 0.39 0.65 1.70 2.83 3-7 1.01 23.71% 10.0%0.16 0.31 0.58 1.94 3.63 3-8 1.00 33.25% 10.0% 0.12 0.25 0.53 2.08 4.423-9 1.00 9.89% 15.1% 0.26 0.41 0.64 1.58 2.46 3-10 1.01 14.00% 15.1%0.20 0.35 0.58 1.75 2.90 3-11 1.00 23.71% 15.1% 0.14 0.27 0.53 1.93 3.793-12 1.00 33.25% 15.1% 0.11 0.23 0.48 2.09 4.36 3-13 1.00 9.89% 20.0%0.22 0.36 0.58 1.64 2.64 3-14 0.99 14.00% 20.0% 0.18 0.31 0.54 1.72 3.003-15 1.01 23.71% 20.0% 0.13 0.25 0.49 1.92 3.77 3-16 0.99 33.25% 20.0%0.10 0.21 0.45 2.10 4.50 3-17 0.99 9.89% 30.0% 0.16 0.27 0.45 1.69 2.813-18 1.00 14.00% 30.0% 0.14 0.25 0.45 1.79 3.21 3-19 1.00 23.71% 30.0%0.10 0.20 0.39 2.00 3.90 3-20 1.00 33.25% 30.0% 0.08 0.17 0.37 2.13 4.63

Example 4

A standard ethylene-glycol rich solution was prepared comprising 90weight percent ethylene glycol (EG), and five weight percent each of1,2-propanediol (1,2-PDO) and 1,2-butanediol (1,2-BDO). Five grams ofthis standard solution was added to a separate glass vial along withfive grams of each of the nonpolar solvents listed in Table 2. Thecontents were mixed vigorously and allowed to settle and separate intotwo clear phases. The phases were analyzed by gas chromatography todetermine EG, 1,2-PDO, 1,2-BDO weight percentages. These analyticalresults were used to calculate partition coefficients and selectivities.All experiments were conducted at room temperature. Results aresummarized in Table 2.

TABLE 2 P(1,2- P(1,2- S(1,2- S(1,2- Ex Solvent P(EG) PDO) BDO) PDO/EG)BDO/EG) 4-1 EA 0.16 0.22 0.30 1.33 1.86 4-2 NBA 0.04 0.06 0.11 1.71 3.014-3 IBA 0.03 0.06 0.10 1.75 3.10 4-4 IPA 0.06 0.10 0.16 1.54 2.47 4-5IBIB 0.01 0.02 0.05 2.13 4.23 4-6 EHA 0.01 0.02 0.04 2.10 4.58 4-7 EP0.05 0.08 0.13 1.62 2.72 4-8 MV 0.03 0.05 0.09 1.70 2.96 4-9 NPP 0.030.05 0.09 1.83 3.28 4-10 MP 0.10 0.14 0.22 1.44 2.16 4-11 MB 0.04 0.070.12 1.65 2.82 4-12 5E2N 0.02 0.12 0.11 7.08 6.57 4-13 MAK 0.07 0.100.17 1.50 2.49 4-14 DIBK 0.02 0.03 0.12 1.60 5.96 4-15 MIPK 0.34 0.410.50 1.21 1.49 4-16 MIAK 0.07 0.11 0.17 1.52 2.48 4-17 TXIB 0.01 0.020.03 1.53 2.90 4-18 MIBK 0.10 0.15 0.23 1.45 2.21 4-19 MTBE 0.05 0.080.15 1.74 3.15 4-20 DIPE 0.01 0.02 0.04 1.66 3.27 4-21 DBE 0.01 0.010.01 1.21 2.56 4-22 DEGDBE 0.03 0.05 0.09 1.54 2.86 4-23 TOL 0.00 0.000.01 0.62 1.26 4-24 MPK 0.40 0.47 0.57 1.18 1.42

Example 5

Water was added to the standard ethylene-glycol rich solution preparedfor Example 4, comprising 90 weight percent ethylene glycol (EG), andfive weight percent each of 1,2-propanediol (1,2-PDO) and 1,2-butanediol(1,2-BDO). The amount of water on a total solution basis was 10 weightpercent (i.e., based on the total weight of diols and water). Five gramsof this water-containing solution was added to a separate glass vialalong with five grams of each of the nonpolar solvents listed in Table3. The contents were mixed vigorously and allowed to settle and separateinto two clear phases. The phases were analyzed by gas chromatography todetermine EG, 1,2-PDO, 1,2-BDO weight percentages. These analyticalresults were used to calculate partition coefficients and selectivities.All experiments were conducted at room temperature. Results aresummarized in Table 3.

TABLE 3 P(1,2- P(1,2- S(1,2- S(1,2- Ex Solvent P(EG) PDO) BDO) PDO/EG)BDO/EG) 5-1 NH 1.09 0.51 1.03 0.47 0.95 5-2 2-EH 0.37 0.51 0.79 1.392.15 5-3 CH 0.67 0.80 1.12 1.19 1.67 5-4 EA 0.10 0.15 0.24 1.45 2.33 5-5NBA 0.03 0.05 0.10 1.87 3.68 5-6 IBA 0.03 0.05 0.09 1.84 3.76 5-7 IPA0.05 0.08 0.14 1.71 3.12 5-8 NPA 0.01 0.02 0.04 2.19 4.77 5-9 IBIB 0.010.02 0.04 2.28 5.25 5-10 EHA 0.03 0.06 0.12 1.83 3.51 5-11 EP 0.02 0.040.08 1.93 4.15 5-12 MV 0.02 0.04 0.08 2.01 4.08 5-13 NPP 0.07 0.10 0.181.58 2.77 5-14 MP 0.03 0.06 0.11 1.85 3.50 5-15 MB 0.02 0.03 0.09 1.755.45 5-16 5E2N 0.04 0.07 0.15 1.68 3.33 5-17 MAK 0.02 0.03 0.12 1.667.39 5-18 DIBK 0.16 0.22 0.34 1.42 2.15 5-19 MIPK 0.05 0.08 0.15 1.703.26 5-20 MIAK 0.01 0.02 0.03 1.52 3.41 5-21 TXIB 0.06 0.11 0.19 1.642.95 5-22 MIBK 0.23 0.33 0.55 1.42 2.37 5-23 IPH 0.04 0.07 0.14 1.803.63 5-24 MTBE 0.01 0.02 0.04 1.56 3.43 5-25 DIPE 0.01 0.01 0.02 0.952.51 5-26 DBE 0.03 0.04 0.09 1.61 3.38 5-27 DEGDBE 0.00 0.00 0.01 0.581.56 5-28 TOL 0.00 0.00 0.01 0.57 1.46 5-29 PC 3.02 2.74 2.24 0.91 0.745-30 MPK 0.18 0.25 0.38 1.39 2.09

Example 6

This example illustrates the effect of increased water content on thepartition coefficients and selectivities of diols. A standardethylene-glycol rich solution was prepared comprising 74.8 weightpercent ethylene glycol (EG), 15 weight percent water, and 1.7 weightpercent each of 1,2-propanediol (1,2-PDO), 1,2-butanediol (1,2-BDO),1,3-propanediol (1,3-PDO), 2,3-butanediol (2,3-BDO), 1,3-butanediol(1,3-BDO), and 1,4-butanediol (1,4-BDO). Ten grams of this standardsolution were added to a separate glass vial along with ten grams ofeach of the hydrophobic solvent mixtures listed in Table 4a. Thecontents were mixed vigorously and allowed to settle and separate intotwo clear phases and analyzed by gas chromatography to determine weightpercentages of each of the diols. These analytical results were used tocalculate partition coefficients (Table 4b) and selectivities (Table4c). All experiments were conducted at 60 degrees Celsius.

TABLE 4a Hydrophobic Hydrophobic Wt % Wt % Ex Solvent 1 Solvent 2Solvent 1 Solvent 2 6-1 EA — 100% 0% 6-2 DIBK — 100% 0% 6-3 MIBK — 100%0% 6-4 2-EH — 100% 0% 6-5 2-EH HEP  90% 10% 6-6 2-EH HEP  80% 20% 6-7 ND— 100% 0% 6-8 ND HEP  90% 10% 6-9 ND HEP  80% 20%

TABLE 4b P(1,2- P(2,3- P(1,3- P(1,2- P(1,3- P(1,4- Ex P(EG) PDO) BDO)PDO) BDO) BDO) BDO) 6-1 0.18 0.27 0.44 0.19 0.41 0.30 0.23 6-2 0.13 0.230.40 0.15 0.38 0.26 0.19 6-3 0.02 0.04 0.29 0.03 0.19 0.06 0.04 6-4 0.020.03 0.31 0.03 0.22 0.05 0.04 6-5 0.11 0.18 0.34 0.13 0.31 0.22 0.16 6-60.07 0.13 0.28 0.09 0.28 0.17 0.12 6-7 0.37 0.53 0.76 0.47 0.79 0.620.52 6-8 0.18 0.34 0.62 0.31 0.66 0.44 0.34 6-9 0.25 0.39 0.67 0.34 0.660.47 0.37

TABLE 4c S(1,2- S(2,3- S(1,3- S(1,2- S(1,3- S(1,4- PDO/ BDO/ PDO/ BDO/BDO/ BDO/ Ex EG) EG) EG) EG) EG) EG) 6-1 1.51 2.42 1.07 2.25 1.65 1.256-2 1.73 3.06 1.15 2.94 1.95 1.45 6-3 1.70 12.15 1.27 7.99 2.56 1.78 6-41.85 16.84 1.45 11.75 2.92 2.30 6-5 1.70 3.15 1.18 2.90 2.06 1.44 6-62.00 4.21 1.31 4.16 2.59 1.83 6-7 1.45 2.07 1.29 2.16 1.68 1.42 6-8 1.863.41 1.73 3.67 2.42 1.88 6-9 1.60 2.71 1.39 2.66 1.92 1.52

Example 7

This example illustrates the effect of increased water content on thepartition coefficients and selectivities of diols. A standardethylene-glycol rich solution was prepared comprising 61.6 weightpercent ethylene glycol (EG), 30 weight percent water, and 1.4 weightpercent each of 1,2-propanediol (1,2-PDO), 1,2-butanediol (1,2-BDO),1,3-propanediol (1,3-PDO), 2,3-butanediol (2,3-BDO), 1,3-butanediol(1,3-BDO), and 1,4-butanediol (1,4-BDO). Ten grams of this standardsolution were added to a separate glass vial along with ten grams ofeach of the hydrophobic solvent mixtures listed in Table 5a. Thecontents were mixed vigorously and allowed to settle and separate intotwo clear phases and analyzed by gas chromatography to determine weightpercentages of each of the diols. These analytical results were used tocalculate partition coefficients (Table 5b) and selectivities (Table5c). All experiments were conducted at 60 degrees Celsius.

TABLE 5a Hydrophobic Hydrophobic Wt % Wt % Ex Solvent 1 Solvent 2Solvent 1 Solvent 2 7-1 EA — 100% 0% 7-2 DIBK — 100% 0% 7-3 MIBK — 100%0% 7-4 2-EH — 100% 0% 7-5 2-EH HEP  90% 10% 7-6 2-EH HEP  80% 20% 7-7 ND— 100% 0% 7-8 ND HEP  90% 10% 7-9 ND HEP  80% 20%

TABLE 5b P(1,2- P(2,3- P(1,3- P(1,2- P(1,3- P(1,4- Ex P(EG) PDO) BDO)PDO) BDO) BDO) BDO) 7-1 0.14 0.27 0.51 0.25 0.55 0.35 0.70 7-2 0.18 0.300.54 0.25 0.52 0.36 0.27 7-3 0.11 0.21 0.43 0.20 0.46 0.28 0.20 7-4 0.280.42 0.65 0.31 0.68 0.48 0.38 7-5 0.15 0.26 0.50 0.18 0.55 0.34 0.26 7-60.20 0.32 0.55 0.22 0.55 0.37 0.29 7-7 0.12 0.23 0.45 0.15 0.48 0.290.22 7-8 0.15 0.26 0.47 0.17 0.47 0.31 0.23 7-9 0.10 0.18 0.38 0.12 0.410.24 0.17

TABLE 5c S(1,2- S(2,3- S(1,3- S(1,2- S(1,3- S(1,4- PDO/ BDO/ PDO/ BDO/BDO/ BDO/ Ex EG) EG) EG) EG) EG) EG) 7-1 1.92 3.69 1.80 3.97 2.51 5.027-2 1.69 3.07 1.44 2.95 2.03 1.53 7-3 2.00 3.98 1.87 4.25 2.58 1.89 7-41.51 2.34 1.11 2.46 1.74 1.38 7-5 1.77 3.32 1.22 3.65 2.27 1.73 7-6 1.592.79 1.12 2.78 1.88 1.44 7-7 1.83 3.59 1.22 3.90 2.36 1.81 7-8 1.67 3.061.12 3.05 1.98 1.46 7-9 1.91 3.92 1.22 4.24 2.48 1.80

Example 8

This example illustrates the back extraction of three-carbon diols andfour-carbon diols from a hydrophobic solvent mixture using water.Hydrophobic solvent and diol mixtures were prepared from 2-EH, HEP, EG,1,2-PDO, 1,2-BDO, 1,3-PDO, 2,3-BDO, 1,3-BDO, and 1,4-BDO. Ten grams ofwater were added to a separate glass vial along with fifteen grams ofeach of the hydrophobic solvent mixture as listed in Table 6a. Thecontents were mixed vigorously and allowed to settle and separate intotwo clear phases and analyzed by gas chromatography to determine weightpercentages of each of the diols. These analytical results were used tocalculate partition coefficients (Table 6b) and selectivities (Table6c). All experiments were conducted at 60 degrees Celsius.

TABLE 6a 1,2- 1,2- 1,3- 1,3- 1,4- 2,3- 2-EH, HEP, PDO, BDO, PDO, BDO,BDO, BDO, EG, Ex wt % wt % wt % wt % wt % wt % wt % wt % wt % 8-1 84.6%9.4% 2.0% 2.0% 0.0% 0.0% 0.0% 0.0% 2.0% 8-2 75.2% 18.8% 2.0% 2.0% 0.0%0.0% 0.0% 0.0% 2.0% 8-3 65.8% 28.2% 2.0% 2.0% 0.0% 0.0% 0.0% 0.0% 2.0%8-4 56.4% 37.6% 2.0% 2.0% 0.0% 0.0% 0.0% 0.0% 2.0% 8-5 77.4% 8.6% 2.0%2.0% 2.0% 2.0% 2.0% 2.0% 2.0% 8-6 68.8% 17.2% 2.0% 2.0% 2.0% 2.0% 2.0%2.0% 2.0% 8-7 60.2% 25.8% 2.0% 2.0% 2.0% 2.0% 2.0% 2.0% 2.0% 8-8 51.6%34.4% 2.0% 2.0% 2.0% 2.0% 2.0% 2.0% 2.0%

TABLE 6b P(1,2- P(1,2- P(1,3- P(1,3- P(1,4- P(2,3- Ex PDO) BDO) PDO)BDO) BDO) BDO) P(EG) 8-1 0.087 0.28 N/A N/A N/A N/A 0.035 8-2 0.075 0.24N/A N/A N/A N/A 0.030 8-3 0.061 0.20 N/A N/A N/A N/A 0.025 8-4 0.0500.17 N/A N/A N/A N/A 0.020 8-5 0.101 0.31 0.11 0.17 0.13 0.19 0.043 8-60.082 0.26 0.09 0.13 0.10 0.16 0.034 8-7 0.069 0.22 0.08 0.11 0.08 0.130.028 8-8 0.056 0.18 0.06 0.09 0.06 0.11 0.022

TABLE 6c S(1,2- S(1,2- S(1,3- S(1,3- S(1,4- S(2,3- PDO/ BDO/ PDO/ BDO/BDO/ BDO/ Ex EG) EG) EG) EG) EG) EG) 8-1 2.47 8.00 N/A N/A N/A N/A 8-22.50 8.11 N/A N/A N/A N/A 8-3 2.49 8.15 N/A N/A N/A N/A 8-4 2.57 8.55N/A N/A N/A N/A 8-5 2.34 7.09 2.63 3.85 3.01 4.34 8-6 2.43 7.57 2.723.91 2.98 4.58 8-7 2.48 7.84 2.76 3.89 2.87 4.73 8-8 2.51 7.89 2.71 3.802.72 4.79

Example 9

This example illustrates a second back extraction of diols from ahydrophobic solvent mixture using water. The hydrophobic top phases fromexamples 8-1 through 8-8 were further contacted with a second aliquot ofwater. Ten grams of water were added to a separate glass vial along witheach of the hydrophobic top phases from examples 8-1 to 8-8 (typicallyabout 13 grams). The contents were mixed vigorously and allowed tosettle and separate into two clear phases and analyzed by gaschromatography to determine weight percentages of each of the diols.These analytical results were used to calculate partition coefficients(Table 7a) and selectivities (Table 7b). In examples 9-3 through 9-8, noEG was remaining in the top layers from the first extractions ofexamples 8-3 through 8-8, so EG-based selectivities could not becalculated. All experiments were conducted at 60 degrees Celsius.

TABLE 7a P(1,2- P(1,2- P(1,3- P(1,3- P(1,4- P(2,3- Ex PDO) BDO) PDO)BDO) BDO) BDO) P(EG) 9-1 0.149 0.39 N/A N/A N/A N/A 0.051 9-2 0.120 0.31N/A N/A N/A N/A 0.038 9-3 0.115 0.27 N/A N/A N/A N/A Not detect 9-40.099 0.22 N/A N/A N/A N/A Not detect 9-5 0.157 0.40 0.56 0.21 0.17 0.26Not detect 9-6 0.136 0.33 0.59 0.17 0.13 0.21 Not detect 8-7 0.116 0.270.62 0.14 0.11 0.18 Not detect 9-8 0.105 0.22 0.64 0.11 0.09 0.14 Notdetect

TABLE 7b S(1,2- S(1,2- S(1,3- S(1,3- S(1,4- S(2,3- PDO/ BDO/ PDO/ BDO/BDO/ BDO/ Ex EG) EG) EG) EG) EG) EG) 9-1 2.90 7.52 N/A N/A N/A N/A 9-23.18 8.19 N/A N/A N/A N/A 9-3 N/A N/A N/A N/A N/A N/A 9-4 N/A N/A N/AN/A N/A N/A 9-5 N/A N/A N/A N/A N/A N/A 9-6 N/A N/A N/A N/A N/A N/A 8-7N/A N/A N/A N/A N/A N/A 9-8 N/A N/A N/A N/A N/A N/A

Example 10

A mixed diol solution was prepared by mixing 1.5 weight percent each of1,2-propanediol (1,2-PDO) and 1,2-butanediol (1,2-BDO), with theremainder ethylene glycol (EG). Three standard water-diol solutions wereprepared by mixing 0 weight percent, 10 weight percent, or 20 weightpercent water with the above mixed diol solution, based on the totalweight of diol and water. Four standard non-polar solutions wereprepared comprising either 1 weight percent, 10 weight percent, 30weight percent, or 50 weight percent Cyanex® 923 solvent (C923), withthe remainder heptane. Another four standard non-polar solutions wereprepared comprising either 1 weight percent, 10 weight percent, 30weight percent, or 50 weight percent C923 solvent, with the remaindertoluene. Ten grams of each of the standard ethylene glycol richsolutions were contacted with ten grams of each of the eight Cyanexstandard solutions in separate glass vials. The contents were mixedvigorously and allowed to settle and separate into two clear phases. Thephases were analyzed by gas chromatography to determine weightpercentages of each of the diols in each phase. These analytical resultswere used to calculate partition coefficients for EG, 1,2-PDO, and1,2-BDO as shown in Tables 8a, 8b, and 8c respectively. Selectivitiesover EG are given in Table 8d and Table 8e for 1,2-PDO and 1,2-BDO,respectively. All experiments were conducted at room temperature.

TABLE 8a wt % C923 in P(EG) w/0% P(EG) w/10% P(EG) w/20% Cosol- solventH2O in Diol H2O in Diol H2O in Diol Ex vent mixture Mixture MixtureMixture 10-1 Heptane 1.0% 0.0016 0.0016 0.0013 10-2 Heptane 10.0% 0.01820.0169 0.0157 10-3 Heptane 30.0% 0.0667 0.0614 0.0554 10-4 Heptane 50.0%0.1268 0.1138 0.1016 10-5 Toluene 1.0% 0.0046 0.0036 0.0033 10-6 Toluene10.0% 0.0342 0.0229 0.0205 10-7 Toluene 30.0% 0.0917 0.0757 0.0662 10-8Toluene 50.0% 0.1575 0.1282 0.1177

TABLE 8b wt % P(1,2-PDO) P(1,2-PDO) P(1,2-PDO) C923 in w/0% H2O w/10%H2O w/20% H2O Cosol- solvent in Diol in Diol in Diol Ex vent mixtureMixture Mixture Mixture 10-1 Heptane 1.0% 0.0034 0.0032 0.0070 10-2Heptane 10.0% 0.0400 0.0402 0.0351 10-3 Heptane 30.0% 0.1275 0.12820.1235 10-4 Heptane 50.0% 0.2241 0.2207 0.2118 10-5 Toluene 1.0% 0.01000.0080 0.0088 10-6 Toluene 10.0% 0.0632 0.0486 0.0440 10-7 Toluene 30.0%0.1581 0.1452 0.1367 10-8 Toluene 50.0% 0.2550 0.2298 0.2286

TABLE 8c wt % P(1,2-BDO) P(1,2-BDO) P(1,2-BDO) C923 in w/0% H2O w/10%H2O w/20% H2O Cosol- solvent in Diol in Diol in Diol Ex vent mixtureMixture Mixture Mixture 10-1 Heptane 1.0% 0.0134 0.0101 0.0211 10-2Heptane 10.0% 0.0879 0.0986 0.1054 10-3 Heptane 30.0% 0.2601 0.29660.3235 10-4 Heptane 50.0% 0.4432 0.4955 0.5301 10-5 Toluene 1.0% 0.02080.0203 0.0000 10-6 Toluene 10.0% 0.1218 0.1117 0.1194 10-7 Toluene 30.0%0.2989 0.3130 0.3341 10-8 Toluene 50.0% 0.4659 0.4812 0.5448

TABLE 8d wt % S(1,2-PDO/ S(1,2-PDO/ S(1,2-PDO/ C923 in EG) w/0% EG)w/10% EG) w/20% Cosol- solvent H2O in Diol H2O in Diol H2O in Diol Exvent mixture Mixture Mixture Mixture 10-1 Heptane 1.0% 2.09 2.06 5.2710-2 Heptane 10.0% 2.20 2.37 2.24 10-3 Heptane 30.0% 1.91 2.09 2.23 10-4Heptane 50.0% 1.77 1.94 2.08 10-5 Toluene 1.0% 2.18 2.23 3.03 10-6Toluene 10.0% 1.84 2.12 2.63 10-7 Toluene 30.0% 1.72 1.92 2.06 10-8Toluene 50.0% 1.62 1.79 1.94

TABLE 8e wt % S(1,2-BDO/ S(1,2-BDO/ S(1,2-BDO/ C923 in EG) w/0% EG)w/10% EG) w/20% Cosol- solvent H2O in Diol H2O in Diol H2O in Diol Exvent mixture Mixture Mixture Mixture 10-1 Heptane 1.0% 8.15 6.45 15.8310-2 Heptane 10.0% 4.83 5.82 6.73 10-3 Heptane 30.0% 3.90 4.83 5.84 10-4Heptane 50.0% 3.49 4.35 5.22 10-5 Toluene 1.0% 4.53 5.66 7.13 10-6Toluene 10.0% 3.56 4.87 5.83 10-7 Toluene 30.0% 3.26 4.13 5.05 10-8Toluene 50.0% 2.96 3.75 4.63

Example 11

An ethylene glycol-rich solution was prepared by mixing 95 weightpercent ethylene glycol, and 2.5 weight percent each of 1,2-propanedioland 1,2-butanediol. The resulting mixed diol feed was subjected to acascaded series of twenty-four cross-flow batch extractions to simulatea six-stage continuous counter-current fractional extraction process,with the mixed diol feed introduced on stage four (from the bottom), thehydrophobic solvent, 2-ethylhexanol (2-EH), introduced on stage one(from bottom), and the water wash on stage six (top of extractor). Themulti-cycle, cascaded pattern of 24 extractions in which one mixed diolfeed charge is added into the center of the first cycle of the cascade,and multiple hydrophobic solvent and water wash charges are introducedat separate ends of each cycle of the cascade, and with raffinate andextract compositions introduced to the next cycle of the cascade,results in a set of conditions on the final cycle which have been shownto closely approach the equilibrium composition profile of a continuous,staged, counter-current fractional extractor. For this work, threecycles were found to be sufficient to asymptotically approach continuousextraction equilibrium conditions. The simulated counter-currentextraction technique used herein is well-known to those skilled in theart and is laid out in detail in Treybal (“Liquid Extraction,” 2nd Ed.,McGraw-Hill Book Company, New York, N.Y., 1963, pp. 349-366). The waterto mixed diol feed weight ratio was 0.4:1.0, and the 2-EH to mixed diolfeed ratio was 1.5:1.0. The experiment was conducted at roomtemperature. The final simulated extract (top product) and raffinate(bottom product) streams were subjected to gas chromatography todetermine the compositions of the products. Results are given in Table9. The percent recovery to the extract is based on the amount of eachcomponent in all inputs to the extractor. The solvent free raffinatecomposition (in weight percent) is calculated based on the total weightof EG, 1,2-PDO, and 1,4-BDO in the raffinate.

TABLE 9 Feed Extract Raffinate Composition Composition % CompositionSolvent Free of Feed, Wt of Extract, Recovery of Raffinate, Composition,% Wt % to Extract Wt % Wt % EG 95.0% 0.26% 0.4% 69.56% 97.0% 1,2-BDO2.5% 1.04% 64.0% 0.66% 0.9% 1,2-PDO 2.5% 0.32% 20.0% 1.47% 2.1% Water2.73% 10.0% 26.32% 2-EH 95.65% 98.2% 1.99%

Example 12

This example illustrates a computer-generated material balance for afractional extraction of a mixed diol feed comprising 95 weight percentEG, 2.5 weight percent 1,2-PDO, and 2.5 weight percent 1,2-BDO. Theextractant for the fractional extraction contains 99.1 weight percent2-ethylhexanol and 0.9 weight percent water. The column comprisesfifteen theoretical stages. The mixed diol feed is fed on stage ten(from the bottom), the extractant, is introduced on stage one (frombottom), and the water wash on stage 15. The water to mixed diol feedweight ratio is 0.53:1.0, and the extractant to mixed diol feed ratio is4.5:1.0. The system was modeled using the Kremser method, as describedin Treybal, Liquid Extraction, 2^(nd) Ed., McGraw Hill Book Company,1963, pp. 248-252, with partition coefficients correlated from the dataof Examples 3 and 6. Material balance (all values in kg/hr) data aregiven in Table 10. Recovery of 1,2-BDO to the extract product is 98.0weight percent. Recovery of EG to the raffinate is 99.95 weight percent.

TABLE 10 1,2- 1,2- Stream ID EG PDO BDO Water 2-EH Total Mixed Diol 952.5 2.5 100.0 Feed Extractant 5.0 450.0 455.0 Water Wash 53.0 53.0 TOTALIN 95 2.5 2.5 58.0 450.0 608.0 Extract 0.04 0.33 2.45 6.0 447.4 456.22Raffinate 94.96 2.17 0.05 52.0 2.6 151.78 TOTAL OUT 95 2.5 2.5 58.0450.0 608.0

Example 13

This example illustrates a computer-generated material balance for afractional extraction of a mixed diol feed comprising 95 weight percentEG, 2.5 weight percent 1,2-PDO, and 2.5 weight percent 1,2-BDO. Theextractant for the fractional extraction contains 80 weight percentCyanex® 923 and 20 weight percent heptane. The column comprises fifteentheoretical stages. The mixed diol feed is fed on stage ten (from thebottom), the extractant is introduced on stage one (from bottom), andthe water wash on stage 15. The water to mixed diol feed weight ratio is0.57:1.0, and the extractant to mixed diol feed ratio is 2.0:1.0. Thesystem was modeled using the Kremser method, as described in Treybal,Liquid Extraction, 2^(nd) Ed., McGraw Hill Book Company, 1963, pp.248-252, with partition coefficients correlated from the data of Example10. Material balance (all values in kg/hr) data are given in Table 11.Recovery of 1,2-BDO to the extract product is 99.7 weight percent.Recovery of EG to the raffinate is 99.95 weight percent.

TABLE 11 1,2- 1,2- Wa- Stream ID EG PDO BDO ter C923 HEP Total MixedDiol 95 2.5 2.5 100.0 Feed Extractant 160.0 40.0 200.0 Water Wash 57.057.0 TOTAL IN 95 2.5 2.5 57.0 160.0 40.0 357.0 Extract 0.05 0.12 2.4917.8 159.99 40.0 220.45 Raffinate 94.95 2.38 0.01 39.2 0.01 0.0 136.55TOTAL OUT 95 2.5 2.5 57.0 160.0 40.0 357.0

Example 14

This example illustrates a computer-generated material balance for thefractional distillation of a mixed diol feed comprising 99.785 weightpercent EG, 0.097 weight percent 1,2-PDO (970 ppm by weight), and 0.118weight percent 1,2-BDO (1180 ppm by weight), derived for example, fromthe hydrogenation of glycolic acid species. One hundred kg/hr of a mixeddiol feed is fed to the eighteenth stage of a distillation columncomprising thirty-six theoretical stages (numbered from the top down), areboiler, and a condenser. The column is operated at 0.2 bar absoluteand the reflux ratio and reboiler heat duty is varied to achieve 80 ppmby mass of 1,2-PDO and 1,2-BDO combined in the EG underflow product.Results are given in Table 12.

TABLE 12 Heat Exam- Reflux Duty, 1,2- 1,2- ple Ratio MJ/hr EG PDO BDO F,Kg/hr 99.785 0.097 0.118 14-1 204.3 352.1 D, Kg/hr 1.701 0.095 0.112 B,Kg/hr 98.084 0.002 0.006 B Purity 99.992% 16 ppm 64 ppm 14-2 480.7 403.4D, Kg/hr 0.75 0.096 0.111 B, Kg/hr 99.035 0.001 0.007 B Purity 99.992%13 ppm 67 ppm 14-3 5432.11 1686.5 D, Kg/hr 0.179 0.097 0.11 B, Kg/hr99.606 0 0.008 B Purity 99.992%  5 ppm 75 ppm

Example 15

This example illustrates a computer-generated material balance for thepre-distillation of a mixed diol feed comprising 99.785 weight percentEG, 0.097 weight percent 1,2-PDO (970 ppm by weight), and 0.118 weightpercent 1,2-BDO (1180 ppm by weight), derived for example, from thehydrogenation of glycolic acid species. One hundred kg/hr of a mixeddiol feed is fed to the eighteenth stage of a distillation columncomprising thirty-six theoretical stages (numbered from the top down), areboiler, and a condenser. The column is operated at 0.2 bar absolute inthe distillate at a mass reflux ratio of 1086:1. Heat duty in thereboiler is calculated as 329 MJ/hr. Material balance (all values inkg/hr) data are given in Table 13. Recovery of 1,2-BDO and 1,2-PDO tothe distillate product are 70 weight percent and 95 weight percent,respectively. Recovery of EG to the bottoms product is 99.8 weightpercent. The purified EG bottoms product consists of 49 ppm by weight1,2-PDO, 347 ppm by weight of 1,2-BDO, and the remainder EG.

TABLE 13 Bottoms Distillate Feed EG 99.592 0.193 99.785 1,2-PDO 0.0050.092 0.097 1,2-BDO 0.035 0.083 0.118

Example 16

This example illustrates a computer-generated material balance for afractional extraction of a mixed diol feed comprising 99.96 weightpercent EG, 49 ppm by weight 1,2-PDO, and 347 ppm by weight 1,2-BDO.This composition is the same as the bottoms product of the distillationstep described in Example 15. The extractant for the fractionalextraction contains 99.1 weight percent 2-ethylhexanol and 0.9 weightpercent water. The column comprises fifteen theoretical stages. Themixed diol feed is fed on stage ten (from the bottom), the extractant isintroduced on stage one (from bottom), and the water wash on stage 15.The water wash to mixed diol feed weight ratio is 0.16:1.0, and theextractant to mixed diol feed ratio is 2.5:1.0. The system was modeledusing the Kremser method, as described in Treybal, Liquid Extraction,2^(nd) Ed., McGraw Hill Book Company, 1963, pp. 248-252, with partitioncoefficients correlated from the data of Examples 3 and 6. Materialbalance (all values in kg/hr) data are given in Table 14. Recovery of1,2-BDO to the extract product is 89.6 weight percent. Recovery of EG tothe raffinate is 99.99 weight percent. The EG product on a solvent-freeand water-free basis comprises 36 ppm by weight 1,2-BDO, 42 ppm byweight of 1,2-PDO, and the remainder EG.

TABLE 14 1,2- 1,2- Stream ID EG PDO BDO Water 2-EH Total Mixed Diol99.59 0.00500 0.03500 99.632 Feed Extractant 2.29 249.08 251.38 WaterWash 15.76 15.76 TOTAL IN 99.59 0.01 0.04 18.05 249.08 366.77 Extract0.0163 0.00078 0.03139 1.00 235.09 236.15 Raffinate 99.58 0.004220.00363 17.05 13.99 130.62 TOTAL OUT 99.59 0.00 0.04 18.05 249.08 366.77

Example 17

This example illustrates a computer-generated material balance for afractional extraction of a mixed diol feed comprising 99.96 weightpercent EG, 49 ppm by weight 1,2-PDO, and 347 ppm by weight 1,2-BDO.This composition is the same as the bottoms product of the distillationstep described in Example 15. The extractant for the fractionalextraction contains 80 weight percent Cyanex® 923 and 20 weight percentdecane. The column comprises fifteen theoretical stages. The mixed diolfeed is fed on stage ten (from the bottom), the extractant, isintroduced on stage one (from bottom), and the water wash on stage 15.The water wash to mixed diol feed weight ratio is 0.36:1.0, and theextractant to mixed diol feed ratio is 1.35:1.0. The system was modeledusing the Kremser method, as described in Treybal, Liquid Extraction,2^(nd) Ed., McGraw Hill Book Company, 1963, pp. 248-252, with partitioncoefficients correlated from the data of Example 10 (i.e., the partitioncoefficients calculated from the 80 weight percent Cyanex® 923 and 20weight percent heptane extractant are used). Material balance (allvalues in kg/hr) data are given in Table 15. Recovery of 1,2-BDO to theextract product is 90.4 weight percent. Recovery of EG to the raffinateis 99.72 weight percent. The EG product on a solvent-free and water-freebasis comprises 34 ppm by weight 1,2-BDO, 48 ppm by weight of 1,2-PDO,and the remainder EG.

TABLE 15 Stream ID EG 1,2-PDO 1,2-BDO Water C923 Decane Total Mixed Diol99.59 0.00500 0.03500 99.632 Feed Extractant 107.60 26.90 134.50 WaterWash 40.82 37.17 TOTAL IN 99.59 0.01 0.04 40.82 107.60 26.90 274.96Extract 0.2746 0.00018 0.03163 11.96 107.59 26.90 146.76 Raffinate 99.320.00482 0.00336 28.86 0.01 0.00 128.20 TOTAL OUT 99.59 0.00 0.03 40.82107.60 26.90 274.96

Example 18

This example illustrates a computer-generated model for the recovery ofthe extracted diols from the extractant solvent mixture by backextraction with water. The extract phase from Example 16, is fed to thebottom stage of an extraction column comprising twelve theoreticalstages. The water back extractant is introduced on stage twelve (frombottom). The water to feed weight ratio is 0.6:1.0. The system wasmodeled using the Kremser method, as described in Treybal, LiquidExtraction, 2^(nd) Ed., McGraw Hill Book Company, 1963, pp. 248-252,with partition coefficients correlated from the data of Example 3 and 6.Material balance (all values in kg/hr) data are given in Table 16.Recovery of 1,2-BDO to the water extract product is 99.93 weightpercent.

TABLE 16 1,2- 1,2- Stream ID EG PDO BDO Water 2-EH Total Extract Phase,0.0163 0.0008 0.0314 1.00 235.09 236.14 Example 16 Extractant 141.690.00 141.69 TOTAL IN 0.0163 0.00 0.03 142.69 235.09 377.83 Extract0.0163 0.00078 0.03137 140.39 0.05 140.49 Raffinate 0.00 0.00000 0.000022.29 235.04 237.33 TOTAL OUT 0.02 0.00 0.03 142.69 235.09 377.83

Example 19

This example illustrates a computer-generated model for the recovery ofthe extracted diols from the extractant solvent mixture by distillation.The extract phase from Example 17, is fed to the eighth stage of afifteen theoretical stage distillation column operated at 150 torr, anda reflux ratio of 2:1. Heterogeneous azeotropes of water, 1,2-PDO,1,2-BDO, and EG with decane (the hydrocarbon component of theextractant,) are distilled as overhead product, allowed to decant intotwo phases, and the hydrocarbon-rich phase is refluxed back to thecolumn. The water layer of the decanter comprising essentially all ofthe EG, 1,2-PDO, 1,2-BDO, and water is continuously removed from thecolumn/decanter. In this fashion, the decane/C923 bottoms product ispurified for recycle to the extraction step of Example 17.

Example 20

This example illustrates a computer-generated model for a single feeddistillation of an EG/1,2-BDO mixed diol feed comprising 80 weightpercent EG and 20 weight percent 1,2-BDO. One hundred kg/hr of theaforementioned mixed diol feed is fed to eighteenth stage of adistillation column comprising thirty-six theoretical stages (numberedfrom the top down), a reboiler, and a condenser. The column is operatedat 0.2 bar absolute in the distillate at a mass reflux ratio of 2.82:1.Heat duty in the reboiler is calculated as 260.4 MJ/hr. Material balance(all values in kg/hr) data are given in Table 17. Recovery of EG to thebottoms product is only 25 weight percent, as the EG/1,2-BDO azeotropeseverely limits the practical separation of EG and 1,2-BDO. The purifiedEG bottoms product consists of 2000 ppm by weight 1,2-BDO and 99.8weight percent EG.

TABLE 17 Bottoms Distillate Feed EG 19.958 60.042 80.0 1,2-BDO 0.0419.960 20.0

Example 21

This example illustrates a computer-generated material balance for afractional extraction of a mixed diol feed comprising 80 weight percentEG and 20 weight percent 1,2-BDO. The extractant for the fractionalextraction contains 99.1 weight percent 2-ethylhexanol and 0.9 weightpercent water. The column comprises fifteen theoretical stages. Themixed diol feed is fed on stage ten (from the bottom), the extractant isintroduced on stage one (from bottom), and the water wash on stage 15.The water wash to mixed diol feed weight ratio is 0.16:1.0, and theextractant to mixed diol feed ratio is 4.3:1.0. The system was modeledusing the Kremser method, as described in Treybal, Liquid Extraction,2^(nd) Ed., McGraw Hill Book Company, 1963, pp. 248-252, with partitioncoefficients correlated from the data of Examples 3 and 6. Materialbalance (all values in kg/hr) data are given in Table 18. Recovery of1,2-BDO to the extract is 99.3 weight percent. Recovery of EG to theraffinate is 99.81 weight percent. The raffinate comprises 0.2 weightpercent 1,2-BDO and 99.8 weight percent EG on a solvent-free andwater-free basis.

TABLE 18 Stream ID EG 1,2-BDO Water 2-EH Total Mixed Diol 80.00 20.00100.00 Feed Extractant 4.30 430.00 434.30 Water Wash 16.10 16.10 TOTALIN 80.00 20.00 20.40 430.00 550.40 Extract 0.15 19.87 1.65 420.93 442.60Raffinate 79.85 0.15 18.75 9.07 107.80 TOTAL OUT 80.0 20.0 20.40 430.00550.40

Example 22

This example illustrates a computer-generated material balance for afractional extraction of a mixed diol feed comprising 80 weight percent1,2-PDO, 20 weight percent 1,2-BDO. The extractant for the fractionalextraction contains 87.5 weight percent Cyanex® 923, 9.72 weight percentheptane, and 2.78 weight percent water. The column comprises fifteentheoretical stages. The mixed diol feed is fed on stage ten (from thebottom), the extractant is introduced on stage one (from bottom), andthe water wash on stage 15. The water wash to mixed diol feed weightratio is 0.795:1.0, and the extractant to mixed diol feed ratio is1.8:1.0. The system was modeled using the Kremser method, as describedin Treybal, Liquid Extraction, 2^(nd) Ed., McGraw Hill Book Company,1963, pp. 248-252, with partition coefficients correlated from the dataof Example 10. Material balance (all values in kg/hr) data are given inTable 19. Recovery of 1,2-BDO to the extract product is 99.87 weightpercent. Recovery of 1,2-PDO to the raffinate is 98.98 weight percent.The raffinate comprises 333 ppm by weight 1,2-BDO and 99.967 1,2-PDO ona solvent-free and water-free basis.

TABLE 19 1,2- 1,2- Stream ID PDO BDO Water C923 HEPT Total Mixed Diol80.00 20.00 100.00 Feed Extractant 5.01 157.50 17.50 180.01 Water Wash79.47 79.47 TOTAL IN 80.00 20.00 84.47 157.50 17.50 359.47 Extract 0.8219.97 14.75 157.48 17.50 210.53 Raffinate 79.18 0.026 69.72 0.02 0.00148.94

Example 23

This example illustrates the separation of diols from aglycerol-containing aqueous mixture. A standard diol/glycerol solutionwas prepared comprising an aqueous solution of 84 weight percent water,10 weight percent glycerol (GLY), 2 weight percent each of ethyleneglycol (EG), 1,2-propanediol (1,2-PDO), and 1,2-butanediol (1,2-BDO).Fifteen grams of this standard solution was added to a separate glassvial along with fifteen grams of each of the nonpolar solvents listed inTable 20. The contents were mixed vigorously and allowed to settle andseparate into two clear phases. The phases were analyzed by gaschromatography to determine glycerol, EG, 1,2-PDO, 1,2-BDO weightpercentages. These analytical results were used to calculate partitioncoefficients and selectivities. All experiments were conducted at roomtemperature. Results are summarized in Table 20.

TABLE 20 P(1,2- P(1,2- S(EG/ S(1,2- S(1,2- Ex Solvent P(EG) PDO) BDO)P(GLY) GLY) PDO/GLY) BDO/GLY) 23-1 n-pentanol 0.19 0.40 1.11 0.07 2.545.44 15.05 23-2 2-EH 0.05 0.13 0.42 0.01 4.99 12.23 38.53 23-3 EA 0.040.10 0.29 0.01 5.31 11.57 34.70 23-4 MIBK 0.02 0.06 0.20 0.00 7.56 18.1064.73 23-5 50 wt % Heptane/ 0.07 0.19 0.74 0.02 3.01 7.68 29.85 50 wt %C923

Example 24

This example illustrates the separation of diols from a glycerol-richaqueous mixture. A standard diol/glycerol solution was preparedcomprising 84 weight percent glycerol (GLY), 10 weight percent water, 2weight percent each of ethylene glycol (EG), 1,2-propanediol (1,2-PDO),and 1,2-butanediol (1,2-BDO). Fifteen grams of this standard solutionwas added to a separate glass vial along with fifteen grams of each ofthe nonpolar solvents listed in Table 21. The contents were mixedvigorously and allowed to settle and separate into two clear phases. Thephases were analyzed by gas chromatography to determine glycerol, EG,1,2-PDO, 1,2-BDO weight percentages. These analytical results were usedto calculate partition coefficients and selectivities. All experimentswere conducted at room temperature. Results are summarized in Table 21.

TABLE 21 P(1,2- P(1,2- S(1,2- S(1,2- Ex Solvent P(EG) PDO) BDO) P(GLY)S(EG/GLY) PDO/GLY) BDO/GLY) 24-1 n-pentanol 0.57 0.97 1.66 0.32 1.763.01 5.14 24-2 2-EH 0.17 0.40 0.89 0.05 3.46 7.85 17.58 24-3 EA 0.080.18 0.41 0.02 4.65 11.10 24.65 24-4 MIBK 0.06 0.14 0.33 0.01 5.51 13.2732.06 24-5 50 wt % Heptane/ 0.18 0.46 1.28 0.07 2.78 6.92 19.28 50 wt %C923

Example 25

This example illustrates the separation of diols from glucose (GLU). Astandard diol/glucose solution was prepared comprising an aqueoussolution of 10 weight percent glucose (GLU), 84 weight percent water, 2weight percent each of ethylene glycol (EG), 1,2-propanediol (1,2-PDO),and 1,2-butanediol (1,2-BDO). Fifteen grams of this standard solutionwas added to a separate glass vial along with fifteen grams of each ofthe nonpolar solvents listed in Table 22. The contents were mixedvigorously and allowed to settle and separate into two clear phases. Thephases were analyzed by gas chromatography to determine glycerol, EG,1,2-PDO, 1,2-BDO weight percentages. These analytical results were usedto calculate partition coefficients and selectivities. All experimentswere conducted at room temperature. Results are summarized in Table 22.

TABLE 22 P(1,2- P(1,2- S(1,2- S(1,2- Ex Solvent P(EG) PDO) BDO) P(GLU)S(EG/GLU) PDO/GLU) BDO/GLU) 25-1 n-pentanol 0.20 0.43 1.21 0.01 15.0232.38  91.20 25-2 2-EH 0.06 0.14 0.46 0.00 ∞ ∞ ∞ 25-3 EA 0.04 0.11 0.320.00 ∞ ∞ ∞ 25-4 MIBK 0.03 0.06 0.21 0.00 ∞ ∞ ∞ 25-5 50 wt % Heptane/0.08 0.20 0.81 0.004 20.51 53.28 213.02 50 wt % C923

What is claimed is:
 1. A process for recovering diols from a mixed diolstream, comprising (A) extracting said mixed diol stream, comprising (i)0.1 weight percent to 50 weight percent of one or more diols selectedfrom the group consisting of ethylene glycol, 1,2-propanediol,1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and2,3-butanediol; (ii) 5 weight percent to 90 weight percent glycerol; and(iii) 5 weight percent to 90 weight percent water; each based on thetotal weight of said mixed diol steam stream, with an extractant,comprising (i) a hydrophobic solvent selected from alkanols having from6 to 20 carbon atoms, ketones having from 5 to 20 carbon atoms, estershaving from 5 to 20 carbon atoms, ethers having from 5 to 20 carbonatoms, carboxylic acids having from 5 to 20 carbon atoms,trialkylphosphine oxides having from 18 to 48 carbon atoms, and mixturesthereof; and (ii) optionally, a second modifying hydrophobic solventselected from hydrocarbons having from 5 to 20 carbon atoms; to form araffinate phase comprising a major amount of said glycerol and a minoramount of said diols contained in said mixed diol stream and an extractphase comprising a major amount of said diols and a minor amount of saidglycerol contained in said mixed diol stream; and (B) separating saidraffinate phase and said extract phase.
 2. The process according toclaim 1 wherein said hydrophobic solvent is selected from2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutyl ketone, methylisopropyl ketone, methyl propyl ketone, diisobutyl ketone,trioctylphosphine oxide, trihexylphosphine oxide, and mixtures thereof.3. The process according to claim 2 wherein greater than 99.5 weightpercent of said glycerol is recovered in said raffinate phase andgreater than 90 weight percent of said diols is recovered in saidextract phase; and wherein said extraction occurs in a continuouscounter-current extractor, wherein said extractant is fed lower to saidextractor than said mixed diol stream, wherein the feed ratio of saidextractant to said mixed diol stream ranges from 0.1:1 to 10:1; furthercomprising feeding a hydrophilic stream to said extractor at a higherlevel than said mixed diol stream, wherein the feed ratio of saidhydrophilic stream to said mixed diol stream ranges from 0.05:1 to2.0:1, and wherein said hydrophilic stream comprises water.
 4. A processfor recovering diols from a mixed diol stream, comprising (A) extractingsaid mixed diol stream, comprising (i) 0.1 weight percent to 30 weightpercent of one or more diols selected from the group consisting ofethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol,1,3-butanediol, 1,4-butanediol, and 2,3-butanediol; (ii) 5 weightpercent to 50 weight percent glucose; and (iii) 50 weight percent to 90weight percent water; each based on the total weight of said mixed diolsteam stream, with an extractant, comprising (i) a hydrophobic solventselected from alkanols having from 6 to 20 carbon atoms, ketones havingfrom 5 to 20 carbon atoms, esters having from 5 to 20 carbon atoms,ethers having from 5 to 20 carbon atoms, carboxylic acids having from 5to 20 carbon atoms, trialkylphosphine oxides having from 18 to 48 carbonatoms, and mixtures thereof; and (ii) optionally, a second modifyinghydrophobic solvent selected from hydrocarbons having from 5 to 20carbon atoms; to form a raffinate phase comprising a major amount ofsaid glycerol and a minor amount of said diols contained in said mixeddiol stream and an extract phase comprising a major amount of said diolsand a minor amount of said glycerol contained in said mixed diol stream;and (B) separating said raffinate phase and said extract phase.
 5. Theprocess according to claim 4 wherein said hydrophobic solvent isselected from 2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutylketone, methyl isopropyl ketone, methyl propyl ketone, diisobutylketone, trioctylphosphine oxide, trihexylphosphine oxide, and mixturesthereof.
 6. The process according to claim 5 wherein greater than 99.5weight percent of said glucose is recovered in said raffinate phase andgreater than 90 weight percent of diols is recovered in said extractphase; and wherein said extraction occurs in a continuouscounter-current extractor, wherein said extractant is fed lower to saidextractor than said mixed diol stream, wherein the feed ratio of saidextractant to said mixed diol stream ranges from 0.1:1 to 10:1; furthercomprising feeding a hydrophilic stream to said extractor at a higherlevel than said mixed diol stream, wherein the feed ratio of saidhydrophilic stream to said mixed diol stream ranges from 0.05:1 to2.0:1, and wherein said hydrophilic stream comprises water.
 7. A processfor recovering purified three-carbon diols from a mixed diol stream,comprising (A) extracting said mixed diol stream, comprising (i) 1weight percent to 99.5 weight of one or more three-carbon diols selectedfrom 1,2-propanediol and 1,3-propanediol; (ii) 20 ppm by weight to 99weight percent of one or more four-carbon diols selected from1,2-butanediol, 1,3-butanediol, 1,4-butanediol, and 2,3-butanediol; eachbased on the total weight of said diols, and (iii) 0 weight percent to50 weight percent water, based on the total weight of said diols andsaid water, with an extractant, comprising (i) a hydrophobic solventselected from alkanols having from 6 to 20 carbon atoms, ketones havingfrom 5 to 20 carbon atoms, esters having from 5 to 20 carbon atoms,ethers having from 5 to 20 carbon atoms, carboxylic acids having from 5to 20 carbon atoms, trialkylphosphine oxides having from 18 to 48 carbonatoms, and mixtures thereof; and (ii) optionally, a second modifyinghydrophobic solvent selected from hydrocarbons having from 5 to 20carbon atoms; to form a raffinate phase comprising a major amount ofsaid three-carbon diols and a minor amount of said four-carbon diolscontained in said mixed diol stream and an extract phase comprising amajor amount of said four-carbon diols and a minor amount of saidthree-carbon diols contained in said mixed diol stream; and (B)separating said raffinate phase and said extract phase.
 8. The processaccording to claim 7 wherein said hydrophobic solvent is selected from2-ethylhexanol, cyclohexanol, n-hexanol, methyl isobutyl ketone, methylisopropyl ketone, methyl propyl ketone, diisobutyl ketone,trioctylphosphine oxide, trihexylphosphine oxide, and mixtures thereof.9. The process according to claim 8 wherein greater than 99.5 weightpercent of said three-carbon diols in said mixed diol stream isrecovered in said raffinate phase and greater than 90 weight percent ofsaid four-carbon diols is recovered in said extract phase; and whereinsaid extraction occurs in a continuous counter-current extractor,wherein said extractant is fed lower to said extractor than said mixeddiol stream, wherein the feed ratio of said extractant to said mixeddiol stream ranges from 0.1:1 to 10:1; further comprising feeding ahydrophilic stream to said extractor at a higher level than said mixeddiol stream, wherein the feed ratio of said hydrophilic stream to saidmixed diol stream ranges from 0.05:1 to 1.5:1, and wherein saidhydrophilic stream comprises water.